leetcode 3Sum Closest

最新推荐文章于 2020-01-16 15:31:01 发布

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最新推荐文章于 2020-01-16 15:31:01 发布

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分类专栏：数据结构与算法

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本文介绍了一种算法，用于在给定数组中找到三个数的和，使得该和与目标数之间的差距最小。通过排序数组并使用双指针技巧，该算法能够高效地解决问题。

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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).

class Solution {
public:
    int threeSumClosest(vector<int> &num, int target) {
         sort(num.begin(), num.end());
        int min =100000, distance = 1000000;
        for(size_t i = 0; i < num.size(); i++)
        {
            int j = i+1;
            int k = num.size() - 1;
            while(j < k)
            {
                if(num[i] + num[j] + num[k] < target)
                {
                    if(abs(num[i] + num[j] + num[k] - target) < distance)
					{
                        min = num[i] + num[j] + num[k];
						distance = abs(min - target);
					}
                    j++;
                }
                else if(num[i] + num[j] + num[k] > target)
                {
                    if(abs(num[i] + num[j] + num[k] - target) < distance)
					{
	                     min = num[i] + num[j] + num[k];
						 distance = abs(min - target);
					}
                        k--;
                }
                else
                {
                    return  target;
                }
            }
        }
        return min;
    }
};