LeetCode Solution 06: 217Invert Binary Tree

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.

判断数组中有无重复数字
利用hash table 可快速实现

way1：

class Solution {public:bool containsDuplicate(vector<int>& nums) {    return nums.size() > set<int>(nums.begin(), nums.end()).size();       }};

way2：

class Solution {unordered_set<int> check;public:bool containsDuplicate(vector<int>& nums) {    if(nums.size() <= 1)        return false;    for(int i = 0; i < nums.size(); i++){        if(check.find(nums[i]) != check.end())            return true;        check.insert(nums[i]);    }    return false;}};