Leetcode: 16. 3Sum Closest

Description

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.

Example

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).

思路

• 找出三个数的和同target最相近的和。
• 同15题类似。记录中间过程出现的最小差值就行

代码

class Solution {
public:
    int threeSumClosest(vector<int>& nums, int target) {
        int len = nums.size();
        if(len <= 2) return 0;
        
        int i = 0, j = 0, k = len - 1;
        int res = 0, min_flag = INT_MAX, sum = res, tmp = 0;
        
        sort(nums.begin(), nums.end());
        for(i = 0; i < len; ++i){
            if(i > 0 && nums[i] == nums[i - 1]) continue;
            
            j = i + 1;
            k = len - 1;
            
            while(j < k){
                if(j > i + 1 && nums[j] == nums[j - 1]){
                    j++;
                    continue;
                }
                if(k < len - 1 && nums[k] == nums[k + 1]){
                    k--;
                    continue;
                }
               
                sum = nums[i] + nums[j] + nums[k];
                tmp = abs(sum - target);
                if(tmp < min_flag){
                    res = sum;
                    min_flag = tmp;
                }
               
                if(sum > target) k--;
                else if(sum < target) j++;
                else return sum;
            }
        }
        
        return res;
    }
};