LeetCode: 3Sum Closest

Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

    For example, given array S = {-1 2 1 -4}, and target = 1.    The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

解析：将3Sum转为2Sum

class Solution {public:    int threeSumClosest(vector<int>& nums, int target) {                sort(nums.begin(), nums.end());                int ans = nums[0] + nums[1] + nums[2];                int i = 0;        while(i < nums.size() - 2)        {            int l = i + 1, r = nums.size() - 1;            int curr_ans = abs(ans - target);            while(l < r)            {                int s = nums[i] + nums[l] + nums[r];                                if (abs(s - target) < curr_ans)                {                    ans = s;                    curr_ans = abs(s - target);                }                if (s > target) {                    r--;                }                else if (s < target){                    l++;                }                else return s;                            }            while(i < nums.size() - 2 && nums[i] == nums[++i]) {};        }                return ans;    }};