Leetcode 3Sum Closest

和3Sum没什么区别，记录最小gap

    int threeSumClosest(vector<int> &num, int target) {        int b, c, n = num.size();        int sum = num[0] + num[1] + num[2];        sort(num.begin(), num.end());        int tmp = 0;        for(int i = 0; i < n-2; i++){           b = i+1; c = n-1;           while(b < c){               tmp = num[i] + num[b] + num[c] ;               if(tmp < target){                   b++;                   if(abs(target - tmp) < abs(sum - target)){                       sum = tmp;                   }               }               else if(tmp > target){                   c--;                   if(abs(target - tmp) < abs(sum - target)){                       sum = tmp;                   }               }               else                    return target;           }        }        return sum;    }