Title
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.
Solution
判断数组元素是否有冗余，就是有重复的，可以用hash表也可以排序后比较相邻两个元素是否相同
//cpp:
class Solution {
public:
bool containsDuplicate(vector<int>& nums) {
unordered_set<int> uset;
for (int i = 0; i < nums.size(); i++) {
if (uset.find(nums[i]) != uset.end()) {
return true;
}
else {
uset.insert(nums[i]);
}
}
return false;
}
};