Java Program for Naive algorithm for Pattern Searching
Given a text txt[0..n-1] and a pattern pat[0..m-1], write a function search(char pat[], char txt[]) that prints all occurrences of pat[] in txt[]. You may assume that n > m.
Examples:
Input: txt[] = "THIS IS A TEST TEXT"
pat[] = "TEST"
Output: Pattern found at index 10
Input: txt[] = "AABAACAADAABAABA"
pat[] = "AABA"
Output: Pattern found at index 0
Pattern found at index 9
Pattern found at index 12
Pattern searching is an important problem in computer science. When we do search for a string in notepad/word file or browser or database, pattern searching algorithms are used to show the search results.
Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.
Java
// Java program for Naive Pattern Searchingpublic class NaiveSearch { public static void search(String txt, String pat) { int M = pat.length(); int N = txt.length(); /* A loop to slide pat one by one */ for (int i = 0; i <= N - M; i++) { int j; /* For current index i, check for pattern match */ for (j = 0; j < M; j++) if (txt.charAt(i + j) != pat.charAt(j)) break; if (j == M) // if pat[0...M-1] = txt[i, i+1, ...i+M-1] System.out.println("Pattern found at index " + i); } } public static void main(String[] args) { String txt = "AABAACAADAABAAABAA"; String pat = "AABA"; search(txt, pat); }}// This code is contributed by Harikishore |
Output:
Pattern found at index 0 Pattern found at index 9 Pattern found at index 13
Time Complexity: O(M * (N – M + 1)), where M and N represents the length of the given strings.
Auxiliary Space: O(1), no extra space is required, so it is a constant.
Please refer complete article on Naive algorithm for Pattern Searching for more details!
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