Leetcode Array 16 3Sum Closest

Posted 2020-09-30 梦_星_空

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).

 这道题目应该是3Sum的一个简化吧，主要也是使用两个指针向中间遍历的方法。代码如下：

public class Solution {
    public int threeSumClosest(int[] nums, int target) {
        int len = nums.length;
        int ans = 0;
        boolean bans = false;
        Arrays.sort(nums);
        for(int i=0;i<len-1;i++){
            if(i>0 && nums[i] == nums[i-1])
                 continue;
            int left = i+1,right = len-1;
            while(left<right){
                int sum = nums[i]+nums[left]+nums[right];
                if(sum == target){
                    return ans = sum;
                }
                else if( sum > target ){
                    right--;
                }
                else{
                    left++;
                }
                if(!bans){
                    ans = sum;
                    bans = true;
                }
                else if( Math.abs(target-ans) > Math.abs(target-sum) ){
                    ans = sum;
                }
            }
        }
        return ans;
    }
}