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3SumClosest.cc
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57 lines (51 loc) · 1.97 KB
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// https://oj.leetcode.com/problems/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).
namespace ThreeSumClosest {
class Solution {
public:
int getClosestSum(vector<int> &num, int i, int start, int end, int target) {
int j = start;
int k = end;
int minDiff = INT_MAX;
int closetSum;
while (j < k) {
if (num[i] + num[j] + num[k] == target) {
return target;
} else if (num[i] + num[j] + num[k] < target) {
int diff = target - num[i] - num[j] - num[k];
if (diff < minDiff) {
minDiff = diff;
closetSum = num[i] + num[j] + num[k];
}
j++;
} else {
int diff = num[i] + num[j] + num[k] - target;
if (diff < minDiff) {
minDiff = diff;
closetSum = num[i] + num[j] + num[k];
}
k--;
}
}
return closetSum;
}
int threeSumClosest(vector<int> &num, int target) {
sort(num.begin(), num.end());
int minDiff = INT_MAX;
int closetSum;
for (int i = 0; i < num.size() - 2; i++) {
int sum = getClosestSum(num, i, i + 1, num.size() - 1, target);
if (abs(target - sum) < minDiff) {
minDiff = abs(target - sum);
closetSum = sum;
}
if (minDiff == 0) {
break;
}
}
return closetSum;
}
};
}