LeetCode——3Sum Closest

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

先排序，然后遍历每一个元素nums[i]，并且在其之后找nums[j]，nums[k]，j<k，使得结果最接近。

sum = nums[i] + nums[j] + nums[k];

if sum > target k--;

if sum < target j++;

if sum == target return;

Code

class Solution {
public:
int threeSumClosest(vector<int>& nums, int target) {
sort(nums.begin(), nums.end());
int minValue = nums[0] + nums[1] + nums[2];
int res = abs(minValue - target);
for (int i = 0; i < nums.size() - 2; i++) {
int j = i + 1;
int k = nums.size() - 1;
while (j < k) {
int sum = nums[i] + nums[j] + nums[k];
if (abs(sum - target) < res) {
res = abs(sum - target);
minValue = sum;
}
if (sum > target)
k--;
else if (sum < target)
j++;
else
return sum;
}
}
return minValue;
}
};