LeetCode-3Sum Closest-三数和最近-有序数组逼近

class Solution {
public:
    int n,m;
    int threeSumClosest(vector<int> &num, int target) {
        vector<int> &a=num;
        n=a.size();
        sort(a.begin(),a.end());
        int ms=numeric_limits<int>::max();
        int res=-1;
        for(int i=0;i<n;i++){
            int x=a[i];
            int l=i+1,r=n-1;
            while(l<r) {
                int cs=x+a[l]+a[r];
                if (abs(cs-target)<ms) {
                    res=cs;
                    ms=abs(cs-target);
                }
                if(cs <target) l++;
                else r--;
            }
        }
        return res;
    }
};