LeetCode #16 最接近的三数之和

class Solution {
public:
    int threeSumClosest(vector<int>& nums, int target) {
        sort(nums.begin(),nums.end());
        int n,i,j,gap,sum,min,ans;
        gap=2147483647;
        n=0;
        while(n<nums.size()-2){
            i=n+1;
            j=nums.size()-1;
            while(i<j){
                sum=nums[n]+nums[i]+nums[j];
                if(abs(target-sum)<gap){
                    gap=abs(target-sum);
                    ans=sum;
                }
                sum<target?i++:j--;
            }
            n++;
            if(gap==0){
                break;
            }
        }
        return ans;
    }
};