LeetCode#217. Contains Duplicate

LeetCode#217.                                                Easy

Contains Duplicate

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

Example 3:

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

Output: true

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Brute Force Approach

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;

}

Sort Approach

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;

}

Hashing Approach

public boolean containsDuplicate(int[] nums) {

    int hash[] = new int[100000];

    for (int x: nums) {

        if (hash[x]>1)

return true;

        hash[x]++;

    }

    return false;

}

HashSet Approach

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;

}