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# Python program to find largest number in a list

Given a list of numbers, the task is to write a Python program to find the largest number in given list.

Examples:

```Input : list1 = [10, 20, 4]
Output : 20```
```Input : list2 = [20, 10, 20, 4, 100]
Output : 100```

Method 1: Sort the list in ascending order and print the last element in the list.

## Python3

 `# Python program to find largest` `# number in a list`   `# list of numbers` `list1 ``=` `[``10``, ``20``, ``4``, ``45``, ``99``]`   `# sorting the list` `list1.sort()`   `# printing the last element` `print``(``"Largest element is:"``, list1[``-``1``])`

Output

`Largest element is: 99`

Time Complexity: O(nlogn)
Auxiliary Space: O(1)

Method 2: Using max() method

## Python3

 `# Python program to find largest` `# number in a list`   `# List of numbers` `list1 ``=` `[``10``, ``20``, ``4``, ``45``, ``99``]`   `# Printing the maximum element` `print``(``"Largest element is:"``, ``max``(list1))`

Output

`Largest element is: 99`

Time complexity : O(n)
Auxiliary Space : O(1)

Method 3: Find the max list element on inputs provided by user

## Python3

 `# Python program to find largest` `# number in a list`   `# Creating an empty list` `list1 ``=` `[]`   `# asking number of elements to put in list` `num ``=` `int``(``input``(``"Enter number of elements in list: "``))`   `# Iterating till num to append elements in list` `for` `i ``in` `range``(``1``, num ``+` `1``):` `    ``ele ``=` `int``(``input``(``"Enter elements: "``))` `    ``list1.append(ele)`   `# Printing maximum element` `print``(``"Largest element is:"``, ``max``(list1))`

Output:

```Enter number of elements in list: 4
Enter elements: 12
Enter elements: 19
Enter elements: 1
Enter elements: 99
Largest element is: 99```

Time complexity : O(n)
Auxiliary Space : O(1)

Method 4: Without using built-in functions in Python:

## Python3

 `# Python program to find largest` `# number in a list`     `def` `myMax(list1):`   `    ``# Assume first number in list is largest` `    ``# initially and assign it to variable "max"` `    ``max` `=` `list1[``0``]` `# Now traverse through the list and compare` `    ``# each number with "max" value. Whichever is` `    ``# largest assign that value to "max'.` `    ``for` `x ``in` `list1:` `        ``if` `x > ``max``:` `            ``max` `=` `x`   `    ``# after complete traversing the list` `    ``# return the "max" value` `    ``return` `max`     `# Driver code` `list1 ``=` `[``10``, ``20``, ``4``, ``45``, ``99``]` `print``(``"Largest element is:"``, myMax(list1))`

Output

`Largest element is: 99`

Time complexity : O(n)
Auxiliary Space : O(1)

Method 5: Use the max() and def functions to find the largest element in a given list. The max() function prints the largest element in the list.

## Python3

 `# Python code to find the largest number` `# in a list` `def` `maxelement(lst):`   `  ``# displaying largest element` `    ``# one line solution` `    ``print``(``max``(lst))`     `# driver code` `# input list` `lst ``=` `[``20``, ``10``, ``20``, ``4``, ``100``]` `# the above input can also be given as` `# lst = list(map(int, input().split()))` `# -> taking input from the user` `maxelement(lst)`

Output

`100`

Time complexity : O(n)
Auxiliary Space : O(1)

## Python3

 `# python code to print largest element in the list`   `lst ``=` `[``20``, ``10``, ``20``, ``4``, ``100``]` `print``(``max``(lst, key``=``lambda` `value: ``int``(value)) )`

Output

`100`

Time complexity : O(n)
Auxiliary Space: O(n), where n is the length of the list.

## Python3

 `from` `functools ``import` `reduce` `lst ``=` `[``20``, ``10``, ``20``, ``4``, ``100``]` `largest_elem ``=` `reduce``(``max``, lst)` `print``(largest_elem)`

Output

`100`

Time Complexity: O(n)
Auxiliary Space: O(1)

## Python3

 `# Function to find the largest element in the list` `def` `FindLargest(itr, ele, list1):`   `  ``# Base condition` `    ``if` `itr ``=``=` `len``(list1):` `        ``print``(``"Largest element in the list is: "``, ele)` `        ``return`   `      ``# Check max condition` `    ``if` `ele < list1[itr]:` `        ``ele ``=` `list1[itr]`   `        ``# Recursive solution` `    ``FindLargest(itr``+``1``, ele, list1)`   `    ``return`   `  ``# input list` `list1 ``=` `[``2``, ``1``, ``7``, ``9``, ``5``, ``4``]`   `FindLargest(``0``, list1[``0``], list1)`

Output

`Largest element in the list is:  9`

Time Complexity: O(n)
Auxiliary Space: O(n)

Method: Using heapq.nlargest()

Here’s how you can use heapq.nlargest() function to find the largest number in a list:

Algorithm:

1. Import the heapq module.
2. Create a list of numbers.
3. Use the heapq.nlargest() function to find the largest element. The nlargest() function takes two arguments – the first argument is the number of largest elements to be returned, and the second argument is the list of numbers.
4. Retrieve the largest element from the list of largest elements returned by heapq.nlargest() function.
5. Print the largest element.

## Python3

 `import` `heapq`   `# list of numbers` `list1 ``=` `[``10``, ``20``, ``4``, ``45``, ``99``]`   `# finding the largest element using heapq.nlargest()` `largest_element ``=` `heapq.nlargest(``1``, list1)[``0``]`   `# printing the largest element` `print``(``"Largest element is:"``, largest_element)`

Output

`Largest element is: 99`

Time complexity: O(nlogk), where n is the length of the list and k is the number of largest elements to be returned. In this case, k is 1, so the time complexity is O(nlog1) = O(n).
Auxiliary Space: O(k), where k is the number of largest elements to be returned. In this case, k is 1, so the auxiliary space is O(1).

Method: Using np.max() method:

Approach:

1. Initialize the test list.
2. Use np.array() method to convert the list to numpy array.
3. Use np.max() method on numpy array which gives the max element in the list.

## Python3

 `import` `numpy as np`   `# given list` `list1 ``=` `[``2``, ``7``, ``5``, ``64``, ``14``]`   `# converting list to numpy array` `arr ``=` `np.array(list1)`   `# finding largest numbers using np.max() method` `num ``=` `arr.``max``()`   `# printing largest number` `print``(num)`

Output:

`64`

Time Complexity: O(n) where n is the length of the list.
Auxiliary Space: O(n) where n is the length of the list. because numpy array of length n is created.

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