leetcode/217. Contain Dublicates at main · 0xShubhamSolanki/leetcode · GitHub

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// 2 loop tc O (n2)
class Solution {
    public boolean containsDuplicate(int[] nums) {
        for (int i = 0; i < nums.length; i++) {
            for (int j = i + 1; j < nums.length; j++) {
                if (nums[i] == nums[j]) return true;
            }
        }
        return false;
    }
}

// Sorting Array TC O(n log n) SC - O(1)
import java.util.*;

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

// hashSet tc -O(n) sc -O(n)
import java.util.*;

class Solution {
    public boolean containsDuplicate(int[] nums) {
        Set<Integer> seen = new HashSet<>();
        for (int num : nums) {
            if (seen.contains(num)) {
                return true; // duplicate found
            }
            seen.add(num);
        }
        return false; // all unique
    }
}