16. 3Sum Closest

原题

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).

代码实现

public int ThreeSumClosest(int[] nums, int target) {
//assert nums.Length>3
//assert have exactly one solution
Array.Sort(nums);
int closet = nums[0] + nums[1] + nums[2] - target;
for (int i = 0; i < nums.Length - 2; i++){
while (i > 0 && i < nums.Length - 2 && nums[i] == nums[i - 1]) i++;
int lo = i + 1, hi = nums.Length - 1;
while (lo < hi){
int tmpcloset = nums[i] + nums[lo] + nums[hi] - target;
if (tmpcloset == 0) return target;
if (tmpcloset < 0)                {
if (-tmpcloset < Math.Abs(closet))
closet = tmpcloset;
lo++;
}
else{//tmpcloset>0
if (tmpcloset < Math.Abs(closet))
closet = tmpcloset;
hi--;
}
}
}
return closet + target;
}

题库

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完成题目索引

http://blog.csdn.net/daigualu/article/details/73008186