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).
Anwser 1: O(n^2)
[cpp]
class Solution {
public:
int threeSumClosest(vector<int> &num, int target) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
int len = num.size();
assert(len >= 3);
vector<int> num2;
num2.assign(num.begin(), num.end());
sort(num2.begin(), num2.end());
int sum = num2[0] + num2[1] + num2[2];
int diff = abs(sum - target);
int ret = sum;
for(int i = 0; i < len - 2; i++){
int l = i + 1;
int r = len - 1;
while(l < r){
sum = num2[i] + num2[l] + num2[r];
if(sum == target) {
return sum;
} else if (sum < target){
l++;
} else {
r--;
}
if(abs(sum - target) < diff){ // more close, refresh diff and ret
diff = abs(sum - target);
ret = sum;
}
}
}
return ret;
}
};
参考推荐:
3Sum
4Sum
数组中最大和的子数组
补充:软件开发 , C++ ,