LeetCode16 3Sum Closest

题意：

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. (Medium)

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).

分析：

　　排序、遍历方式顺序 与3 sum思路一致，维护一个与target的差值即可。

代码：

class Solution {
public:
int threeSumClosest(vector<int>& nums, int target) {
sort(nums.begin(), nums.end());
int diff = 0x7FFFFFFF;
for (int i = 0; i < nums.size() - 2; ++i) {
int start = i + 1, end = nums.size() - 1;
while (start < end) {
int curSum = nums[i] + nums[start] + nums[end];
if (curSum - target == 0) {
return target;
}
else if (curSum - target > 0) {
if (curSum- target < abs(diff) ) {
diff = curSum - target;
}
end--;
}
else {
if (target - curSum < abs(diff)) {
diff = curSum - target;
}
start++;
}
}
}
return diff + target;
}
};