class Solution { public: //双指针算法 int findRepeatNum(vector<int>& nums) { sort(nums.begin(),nums.end()); int n=nums.size(); int left=0,right=n-1; while(nums[left]!=nums[left+1])left++; while(nums[right]!=nums[right-1])right--; return nums[right];//返回right和left都一样 } };