3SumClosest
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)
class Solution { public: int threeSumClosest(vector<int> &num, int target) { int res = INT_MAX; int N = num.size(); sort(num.begin(), num.end()); for (int i = 0; i < N-2; ++i) { int l = i + 1, r = N - 1; while (l < r) { int threesum = num[i] + num[l] + num[r]; if (threesum == target) return target; else if (threesum < target) l++; else r--; if (res == INT_MAX || abs(threesum - target) < abs(res - target)) // overflow tricky res = threesum; } } return res; } };