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Contains duplicates

 Given an array of integers, find if the array contains any duplicates.

Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct.

Example 1

Input: [1,2,3,1]
Output: true


Example 2

Input: [1,2,3,4]
Output: false

Java

1. Using Linear search (takes more time)

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public boolean containsDuplicate(int[] nums) {
    for (int i = 0; i < nums.length; ++i) {
        for (int j = 0; j < i; ++j) {
            if (nums[j] == nums[i]) return true;  
        }
    }
    return false;
 }

2. Using sorting

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public boolean containsDuplicate(int[] nums) {
    Arrays.sort(nums);
    for (int i = 0; i < nums.length - 1; ++i) {
        if (nums[i] == nums[i + 1]) 
           return true;
    }
    return false;
 }

3. Using HashSet

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public boolean containsDuplicate(int[] nums) {
    Set<Integer> set = new HashSet<>(nums.length);
    for (int x: nums) {
        if (set.contains(x)) 
            return true;
        set.add(x);
    }
    return false;
 }

Python

1. Using Linear search (takes more time)

def containsDuplicate(arr):
    for i in range(0, len(arr)):
        if arr[i] in arr[i+1:]:
            return True
    return False

2. Using sorting 

def containsDuplicate(arr):
    arr.sort()
    for i in range(0, len(arr)-1):
        if arr[i]==arr[i+1]:
            return True
    return False

3. Using Set

def containsDuplicate(arr):
    if len(arr) != len(set(arr)):
        return True
    return False


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