Leetcode——16. 3Sum Closest

曾经终败给现在 2022-06-14 09:26 118阅读 0赞

## 1. 概述 ##

### 1.1 题目 ###

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).

### 1.2 解题思路 ###

这道题跟之前的3Sum问题很相似，就是求取数组中跟目标值最近的。在计算过程中将每一个可能的结果与目标值最接近的记录下来，最后便得到了需求的解。

## 2.  编码 ##

class Solution {
    public:
        int threeSumClosest(vector<int>& nums, int target) {
            int len(nums.size());   //得到数组的长度
            sort(nums.begin(), nums.end());
            if(nums[0]==nums[len-1]) return 3*nums[0];
            if(3 == len) return (nums[0]+nums[1]+nums[2]);
            
            int min_sum(123456789), left(0), right(0),res(0);
            for(int i=0; i<len-2; ++i)
            {
                int temp_target = target - nums[i];
                left = i+1;
                right = len-1;
                while(left < right)
                {
                    int sum = temp_target - nums[left] - nums[right];
                    if(sum == 0) return target;
                    if(sum > 0)
                    {
                        if(abs(sum)<abs(min_sum))
                        {
                            res = nums[left]+nums[right]+nums[i];   //记录与目标值最接近的值
                            min_sum = sum;
                        }
                        ++left;
                    }
                    if(sum < 0)
                    {
                        if(abs(sum)<abs(min_sum))
                        {
                            res = nums[left]+nums[right]+nums[i];
                            min_sum = sum;
                        }
                        --right;
                    }
                }
            }
            
            return res;
        }
    };