第64题 3Sum Closest

最新推荐文章于 2020-12-26 15:24:26 发布

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本文介绍了一个算法问题：给定一个整数数组和一个目标值，找到数组中三个整数的和最接近目标值的方法。提供了一种解决方案，通过先排序数组，然后使用双指针技巧遍历数组并调整指针位置来逐步逼近目标值。

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).

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Solution in C++:

class Solution {
public:
    int threeSumClosest(vector<int>& nums, int target) {
        int result=0;
        if(nums.size()<=3){
            for(int i=0; i<nums.size(); i++) result+=nums[i];
            return result;
        }
        sort(nums.begin(), nums.end());
        
        result = nums[0]+nums[1]+nums[2];
        int sum;
        for(int i=0; i<nums.size()-2; i++){
            int start = i+1, end = nums.size()-1;
            while(start<end){
              sum = nums[i]+nums[start]+nums[end];
              if(sum==target) return target;
              else if(sum<target) start++;
              else  end--;
              result = abs(result-target)<=abs(sum-target)?result:sum;
            }
            while(nums[i+1]==nums[i]&&i+1<nums.size()) i++;
        }
        return result;
    }
};