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Subset with sum divisible by m

• Difficulty Level : Hard
• Last Updated : 06 Feb, 2023

Given a set of non-negative distinct integers, and a value m, determine if there is a subset of the given set with sum divisible by m.
Input Constraints
Size of set i.e., n <= 1000000, m <= 1000
Examples:

Input : arr[] = {3, 1, 7, 5};
m = 6;
Output : YES

Input : arr[] = {1, 6};
m = 5;
Output : NO

This problem is a variant of subset sum problem. In subset sum problem we check if given sum subset exists or not, here we need to find if there exists some subset with sum divisible by m or not.

Naive Approach( Using Recursion) :

C++

 // C++ program to check if there is a subset // with sum divisible by m. #include using namespace std;   // Returns true if there is a subset // of arr[] with sum divisible by m bool helper(int N, int nums[], int sum, int idx, int m){     // if we reach last index     if(idx == N){         // and if the sum mod m is zero         if(sum && sum%m == 0){             // return               return true ;         }         return false ;     }       // 2 choices - to pick or to not pick     bool picked    = helper(N, nums, sum+nums[idx], idx+1,m) ;     bool notPicked = helper(N, nums, sum,          idx+1, m) ;       return picked || notPicked ; }   bool modularSum(int arr[], int n, int m) {     return helper(n, arr, 0, 0, m) ; }   // Driver code int main() {     int arr[] = {1, 7};     int n = sizeof(arr)/sizeof(arr[0]);     int m = 5;       modularSum(arr, n, m) ?  cout << "YES\n" :                              cout << "NO\n";       return 0; }

Java

 // Java program to check if there is a subset // with sum divisible by m.   class GFG {     // Returns true if there is a subset   // of arr[] with sum divisible by m   public static boolean helper(int N, int[] nums, int sum,                                int idx, int m)   {     // if we reach last index     if (idx == N)     {         // and if the sum mod m is zero       if ((sum > 0) && (sum % m == 0)) {         // return         return true;       }       return false;     }       // 2 choices - to pick or to not pick     boolean picked       = helper(N, nums, sum + nums[idx], idx + 1, m);     boolean notPicked       = helper(N, nums, sum, idx + 1, m);       return picked || notPicked;   }     public static boolean modularSum(int[] arr, int n,                                    int m)   {     return helper(n, arr, 0, 0, m);   }     // driver code   public static void main(String[] args)   {     int arr[] = { 1, 7 };     int n = arr.length;     int m = 5;       if (modularSum(arr, n, m))       System.out.print("YES\n");     else       System.out.print("NO\n");   } }   // this code is contributed by phasing17

Python3

 # Python3 program to check if there is a subset # with sum divisible by m.   # Returns true if there is a subset # of arr[] with sum divisible by m def helper(N, nums, sum, idx, m):       # if we reach last index     if(idx == N):               # and if the sum mod m is zero         if(sum and sum%m == 0):               # return             return True               return False       # 2 choices - to pick or to not pick     picked    = helper(N, nums, sum+nums[idx], idx+1,m)     notPicked = helper(N, nums, sum,          idx+1, m)       return picked or notPicked   def modularSum(arr, n, m):     return helper(n, arr, 0, 0, m)   # Driver code arr = [1, 7] n = len(arr) m = 5   print("YES") if modularSum(arr, n, m) else print("NO")   # This code is contributed by shinjanpatra.

C#

 // C# program to check if there is a subset // with sum divisible by m. using System;   class GFG {     // Returns true if there is a subset   // of arr[] with sum divisible by m   public static bool helper(int N, int[] nums, int sum,                             int idx, int m)   {     // if we reach last index     if (idx == N) {         // and if the sum mod m is zero       if ((sum > 0) && (sum % m == 0)) {         // return         return true;       }       return false;     }       // 2 choices - to pick or to not pick     bool picked       = helper(N, nums, sum + nums[idx], idx + 1, m);     bool notPicked = helper(N, nums, sum, idx + 1, m);       return picked || notPicked;   }     public static bool modularSum(int[] arr, int n, int m)   {     return helper(n, arr, 0, 0, m);   }     // driver code   public static void Main(string[] args)   {     int[] arr = { 1, 7 };     int n = arr.Length;     int m = 5;       if (modularSum(arr, n, m))       Console.Write("YES\n");     else       Console.Write("NO\n");   } }   // this code is contribyted by phasing17

Javascript



Output

NO

Time Complexity: O(2N)

Auxiliary Space: O(2N)

Memoization Approach: As this contains overlapping subproblems so instead of calling the same function again and again we will store it in a 2D array.
It follows the recursive approach but in this method, we use a 2D matrix that is initialized by -1 or any negative value.
The 2D matrix is used for memorization purpose to avoid repeated recursive calls from the same state.

Below is the implementation of the approach.

C++

 // C++ program to check if there is a subset // with sum divisible by m.   #include using namespace std;   // Returns true if there is a subset // of arr[] with sum divisible by m bool helper(int N, int nums[], int sum, int idx,             int m, vector >& dp) {     // if we reach last index     if (idx == N) {         // and if the sum mod m is zero         if (sum && sum % m == 0) {             // return             return true;         }         return false;     }     if (dp[idx][sum] != -1) {         return dp[idx][sum];     }         // 2 choices - to pick or to not pick     bool picked         = helper(N, nums, sum + nums[idx],                  idx + 1, m, dp);     bool notPicked = helper(N, nums, sum,                             idx + 1, m, dp);       return dp[idx][sum] = picked || notPicked; }   bool modularSum(int arr[], int n, int m) {     int sum = 0;     for (int i = 0; i < n; i++) {         sum += arr[i];     }     vector > dp(n, vector(sum + 1,                                            -1));       return helper(n, arr, 0, 0, m, dp); }   // Driver code int main() {     int arr[] = { 1, 7 };     int n = sizeof(arr) / sizeof(arr[0]);     int m = 5;       modularSum(arr, n, m) ? cout << "YES\n"                           : cout << "NO\n";       return 0; } // This code is contributed by Sanskar

Java

 // Java program to check if there is a subset // with sum divisible by m.   import java.util.Arrays; class GFG {       // Returns true if there is a subset     // of arr[] with sum divisible by m     public static boolean helper(int N, int[] nums, int sum,                                  int idx, int m, int dp[][])     {         // if we reach last index         if (idx == N) {               // and if the sum mod m is zero             if ((sum > 0) && (sum % m == 0)) {                 // return                 return true;             }             return false;         }         if (dp[idx][sum] != -1) {             return dp[idx][sum] == 0 ? false : true;         }         // 2 choices - to pick or to not pick         boolean picked = helper(N, nums, sum + nums[idx],                                 idx + 1, m, dp);         boolean notPicked             = helper(N, nums, sum, idx + 1, m, dp);           dp[idx][sum] = notPicked || picked ? 1 : 0;         return notPicked || picked;     }       public static boolean modularSum(int[] arr, int n,                                      int m)     {           int sum = 0;         for (int i = 0; i < n; i++) {             sum += arr[i];         }         int dp[][] = new int[n][sum + 1];         for (int row[] : dp) {             Arrays.fill(row, -1);         }           return helper(n, arr, 0, 0, m, dp);     }       // Driver code     public static void main(String[] args)     {         int arr[] = { 1, 7 };         int n = arr.length;         int m = 5;           if (modularSum(arr, n, m))             System.out.print("YES\n");         else             System.out.print("NO\n");     } }   // This code is contributed by Sanskar

Python3

 # Python program to check if there is a subset # with sum divisible by m.   # Returns true if there is a subset # of arr[] with sum divisible by m def helper(N, nums, sum, idx, m, dp):         # if we reach last index     if idx == N:                 # and if the sum mod m is zero         if sum and sum % m == 0:             # return             return True         return False     if dp[idx][sum] != -1:         return dp[idx][sum]         # 2 choices - to pick or to not pick     picked = helper(N, nums, sum + nums[idx], idx + 1, m, dp)     notPicked = helper(N, nums, sum, idx + 1, m, dp)       dp[idx][sum] = picked or notPicked     return dp[idx][sum]   def modularSum(arr, n, m):     sum = 0     for i in range(n):         sum += arr[i]     dp = [[-1] * (sum + 1) for i in range(n)]       return helper(n, arr, 0, 0, m, dp)   # Driver code arr = [1, 7] n = len(arr) m = 5   print("YES") if modularSum(arr, n, m) else print("NO")   # This code is contributed by phasing17

C#

 // C# program to check if there is a subset // with sum divisible by m.   using System; using System.Collections.Generic;   class GFG {       // Returns true if there is a subset     // of arr[] with sum divisible by m     public static bool helper(int N, int[] nums, int sum,                               int idx, int m, int[][] dp)     {         // if we reach last index         if (idx == N) {               // and if the sum mod m is zero             if ((sum > 0) && (sum % m == 0)) {                 // return                 return true;             }             return false;         }         if (dp[idx][sum] != -1) {             return dp[idx][sum] == 0 ? false : true;         }         // 2 choices - to pick or to not pick         bool picked = helper(N, nums, sum + nums[idx],                              idx + 1, m, dp);         bool notPicked             = helper(N, nums, sum, idx + 1, m, dp);           dp[idx][sum] = notPicked || picked ? 1 : 0;         return notPicked || picked;     }       public static bool modularSum(int[] arr, int n, int m)     {           int sum = 0;         for (int i = 0; i < n; i++) {             sum += arr[i];         }         int[][] dp = new int[n][];         for (int i = 0; i < n; i++) {             dp[i] = new int[sum + 1];             Array.Fill(dp[i], -1);         }           return helper(n, arr, 0, 0, m, dp);     }       // Driver code     public static void Main(string[] args)     {         int[] arr = { 1, 7 };         int n = arr.Length;         int m = 5;           // Function call         if (modularSum(arr, n, m))             Console.Write("YES\n");         else             Console.Write("NO\n");     } }   // This code is contributed by phasing17

Javascript



Output

NO

Time Complexity: O(N*sum) where sum is the sum of the array elements.
Auxiliary Space: O(N*sum)

Efficient Approach:

Seeing input constraint, it looks like typical DP solution will work in O(nm) time. But in tight time limits in competitive programming, the solution may work. Also auxiliary space is high for DP table, but here is catch.
If n > m there will always be a subset with sum divisible by m (which is easy to prove with pigeonhole principle). So we need to handle only cases of n <= m .
For n <= m we create a boolean DP table which will store the status of each value from 0 to m-1 which are possible subset sum (modulo m) which have been encountered so far.
Now we loop through each element of given array arr[], and we add (modulo m) j which have DP[j] = true, and store all the such (j+arr[i])%m possible subset-sum in a boolean array temp, and at the end of iteration over j, we update DP table with temp. Also we add arr[i] to DP ie.. DP[arr[i]%m] = true.
In the end if DP[0] is true then it means YES there exists a subset with sum which is divisible by m, else NO.

C++

 // C++ program to check if there is a subset // with sum divisible by m. #include using namespace std;   // Returns true if there is a subset // of arr[] with sum divisible by m bool modularSum(int arr[], int n, int m) {     if (n > m)         return true;       // This array will keep track of all     // the possible sum (after modulo m)     // which can be made using subsets of arr[]     // initialising boolean array with all false     bool DP[m];     memset(DP, false, m);       // we'll loop through all the elements of arr[]     for (int i=0; i

Java

 // Java program to check if there is a subset // with sum divisible by m. import java.util.Arrays;   class GFG {           // Returns true if there is a subset     // of arr[] with sum divisible by m     static boolean modularSum(int arr[],                                 int n, int m)     {         if (n > m)             return true;               // This array will keep track of all         // the possible sum (after modulo m)         // which can be made using subsets of arr[]         // initialising boolean array with all false         boolean DP[]=new boolean[m];                   Arrays.fill(DP, false);               // we'll loop through all the elements         // of arr[]         for (int i = 0; i < n; i++)         {                           // anytime we encounter a sum divisible             // by m, we are done             if (DP[0])                 return true;                   // To store all the new encountered sum             // (after modulo). It is used to make             // sure that arr[i] is added only to             // those entries for which DP[j]             // was true before current iteration.             boolean temp[] = new boolean[m];             Arrays.fill(temp, false);                   // For each element of arr[], we loop             // through all elements of DP table             // from 1 to m and we add current             // element i. e., arr[i] to all those             // elements which are true in DP table             for (int j = 0; j < m; j++)             {                                   // if an element is true in                 // DP table                 if (DP[j] == true)                 {                     if (DP[(j + arr[i]) % m] == false)                               // We update it in temp and update                         // to DP once loop of j is over                         temp[(j + arr[i]) % m] = true;                 }             }                   // Updating all the elements of temp             // to DP table since iteration over             // j is over             for (int j = 0; j < m; j++)                 if (temp[j])                     DP[j] = true;                         // Also since arr[i] is a single             // element subset, arr[i]%m is one             // of the possible sum             DP[arr[i] % m] = true;         }               return DP[0];     }           //driver code     public static void main(String arg[])     {         int arr[] = {1, 7};         int n = arr.length;         int m = 5;               if(modularSum(arr, n, m))             System.out.print("YES\n");         else             System.out.print("NO\n");     } }   //This code is contributed by Anant Agarwal.

Python3

 # Python3 program to check if there is # a subset with sum divisible by m.   # Returns true if there is a subset # of arr[] with sum divisible by m def modularSum(arr, n, m):       if (n > m):         return True       # This array will keep track of all     # the possible sum (after modulo m)     # which can be made using subsets of arr[]     # initialising boolean array with all false     DP = [False for i in range(m)]       # we'll loop through all the elements of arr[]     for i in range(n):               # anytime we encounter a sum divisible         # by m, we are done         if (DP[0]):             return True           # To store all the new encountered sum (after         # modulo). It is used to make sure that arr[i]         # is added only to those entries for which DP[j]         # was true before current iteration.         temp = [False for i in range(m)]           # For each element of arr[], we loop through         # all elements of DP table from 1 to m and         # we add current element i. e., arr[i] to         # all those elements which are true in DP         # table         for j in range(m):                       # if an element is true in DP table             if (DP[j] == True):                               if (DP[(j + arr[i]) % m] == False):                       # We update it in temp and update                     # to DP once loop of j is over                     temp[(j + arr[i]) % m] = True                       # Updating all the elements of temp         # to DP table since iteration over         # j is over         for j in range(m):             if (temp[j]):                 DP[j] = True           # Also since arr[i] is a single element         # subset, arr[i]%m is one of the possible         # sum         DP[arr[i] % m] = True           return DP[0]   # Driver code arr = [1, 7] n = len(arr) m = 5 print("YES") if(modularSum(arr, n, m)) else print("NO")   # This code is contributed by Anant Agarwal.

C#

 // C# program to check if there is // a subset with sum divisible by m. using System;   class GFG {       // Returns true if there is a subset // of arr[] with sum divisible by m static bool modularSum(int []arr, int n,                                   int m) {     if (n > m)         return true;        // This array will keep track of all     // the possible sum (after modulo m)     // which can be made using subsets of arr[]     // initialising boolean array with all false     bool []DP=new bool[m];     for (int l=0;l

PHP

 \$m)         return true;       // This array will keep track of all     // the possible sum (after modulo m)     // which can be made using subsets of arr[]     // initialising boolean array with all false     \$DP = Array_fill(0, \$m, false);       // we'll loop through all the elements of arr[]     for (\$i = 0; \$i < \$n; \$i++)     {         // anytime we encounter a sum divisible         // by m, we are done         if (\$DP[0])             return true;           // To store all the new encountered sum         // (after modulo). It is used to make         // sure that arr[i] is added only to those          // entries for which DP[j] was true before         // current iteration.         \$temp = array_fill(0, \$m, false) ;           // For each element of arr[], we loop through         // all elements of DP table from 1 to m and         // we add current element i. e., arr[i] to         // all those elements which are true in DP         // table         for (\$j = 0; \$j < \$m; \$j++)         {             // if an element is true in DP table             if (\$DP[\$j] == true)             {                 if (\$DP[(\$j + \$arr[\$i]) % \$m] == false)                       // We update it in temp and update                     // to DP once loop of j is over                     \$temp[(\$j + \$arr[\$i]) % \$m] = true;             }         }           // Updating all the elements of temp         // to DP table since iteration over         // j is over         for (\$j = 0; \$j < \$m; \$j++)             if (\$temp[\$j])                 \$DP[\$j] = true;           // Also since arr[i] is a single element         // subset, arr[i]%m is one of the possible         // sum         \$DP[\$arr[\$i] % \$m] = true;     }       return \$DP[0]; }   // Driver Code \$arr = array(1, 7); \$n = sizeof(\$arr); \$m = 5;   if (modularSum(\$arr, \$n, \$m) == true )     echo "YES\n"; else     echo "NO\n";   // This code is contributed by Ryuga ?>

Javascript



Output

NO

Time Complexity : O(m^2)
Auxiliary Space : O(m)
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