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3Sum_Closest.cpp
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3Sum_Closest.cpp
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/*
Author: Timon Cui, timonbaby@163.com
Title: 3Sum Closest
Description:
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).
Difficulty rating:
Notes:
O(n^2), similar to the 3Sum problem.
With large numbers as input, the code may overflow. Not handled here for simplicity.
For example, when sum = INT_MAX and target = INT_MIN, sum - target will overflow.
*/
class Solution {
public:
int threeSumClosest(vector<int> &num, int target) {
sort(num.begin(), num.end());
int closest_sum = 0, distance = -1;
for (int i = 0; i < num.size() - 2; ++i) {
int L = i + 1, H = num.size() - 1;
while (L < H) {
int sum = num[i] + num[L] + num[H];
if (sum > target) H --;
else if (sum < target) L ++;
else return target;
if (distance < 0 || abs(sum - target) < distance) {
closest_sum = sum;
distance = abs(sum - target);
}
}
}
return closest_sum;
}
};