【一次过】Lintcode 1320. Contains Duplicate

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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.

样例

Given nums = [1,1], return ture.

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解题思路1：

采用HashSet来判断是否出现过重复元素。

时间复杂度：O(n)

空间复杂度：O(n)

public class Solution {
    /**
     * @param nums: the given array
     * @return: if any value appears at least twice in the array
     */
    public boolean containsDuplicate(int[] nums) {
        // Write your code here
        Set<Integer> set = new HashSet<>();
        
        for(int num : nums){
            if(set.contains(num))
                return true;
            else
                set.add(num);
        }
        
        return false;
    }
}

解题思路2：

先排序，再按位比较。

时间复杂度：O(nlogn)

空间复杂度：O(1)

public class Solution {
    /**
     * @param nums: the given array
     * @return: if any value appears at least twice in the array
     */
    public boolean containsDuplicate(int[] nums) {
        // Write your code here
        if(nums==null || nums.length<2)
            return false;
        
        Arrays.sort(nums);
        
        for(int i=1; i<nums.length ; i++){
            if(nums[i] == nums[i-1])
                return true;
        }
        
        return false;
    }
}