【LeetCode】217. Contains Duplicate 解題報告

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217. Contains Duplicate / Medium

Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.

Example 1:

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

Example 2:

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

Example 3:

Input: nums = [1,1,1,3,3,4,3,2,4,2]
Output: true

Constraints:

  • 1 <= nums.length <= 10^5
  • 10^9 <= nums[i] <= 10^9

Solution

思路

先排序，再檢查前後兩個元素是不是相等，相等就是有重複，可以直接回傳 true，迴圈結束的話就代表沒有重複，回傳 false。

效能

Complexity

  • Time Complexity: O(NlogN)
  • Space Complexity: O(1)

LeetCode Result

Code

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class Solution {
public:
    bool containsDuplicate(vector<int>& nums) {
        sort(nums.begin(), nums.end());
        int n = nums.size();
        for(int i = 1; i < n; ++i) {
            if(nums[i] == nums[i-1]) return true;
        }
        return false;
    }
};