Question
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).
Solution
#include <vector>
#include <algorithm>
#include <cmath>
#include <climits>
using namespace std;
class Solution {
public:
int threeSumClosest(vector<int>& nums, int target) {
sort(nums.begin(), nums.end(), less<int>());
vector<int>::iterator it0, it1, it2;
int closest = INT_MAX;
int distance = INT_MAX;
for (it0 = nums.begin(); it0 < nums.end(); it0++) {
it1 = it0 + 1;
it2 = nums.end() - 1;
while (it1 < it2) {
int sum = *it0 + *it1 + *it2;
if (abs(sum - target) < distance) {
closest = sum;
distance = abs(sum - target);
}
if (sum < target) {
it1++;
} else if (sum > target) {
it2--;
} else {
// equal is the closest
return sum;
}
}
}
return closest;
}
};