判断数组中是否有重复的元素
bool containsDuplicate(vector<int>& nums) {
return !(nums.size() == unordered_set<int>(nums.cbegin(), nums.cend()).size());
}
bool containsDuplicate(vector<int>& nums) {
return !(nums.size() == unordered_set<int>(nums.cbegin(), nums.cend()).size());
}