Leercode 16: 3Sum Closest

转载于 2019-07-21 09:55:30 发布 · 103 阅读

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本文介绍了一种寻找数组中三个整数之和最接近给定目标值的有效算法，并提供了一个C++实现示例。该算法首先对数组进行排序，然后使用双指针技巧遍历数组以找到最优解。

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Given an array nums of n integers and an integer target, find three integers in nums such that the sum is closest to target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

Example:

Given array nums = [-1, 2, 1, -4], and target = 1.

The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

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