CodeForce 710B Optimal Point on a Line

最新推荐文章于 2019-09-05 11:23:59 发布

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最新推荐文章于 2019-09-05 11:23:59 发布

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原文链接：http://www.cnblogs.com/lyf-acm/p/5798173.html

本文介绍了一个经典问题：在给定的离散点集上找到一个点，使得所有其他点到该点的距离之和最小。通过简单的数学分析，文章指出了解决这个问题的有效方法是找到这些点的中位数。

Optimal Point on a Line

　　You are given n points on a line with their coordinates x_i. Find the point x so the sum of distances to the given points is minimal.

Input

　　The first line contains integer n (1 ≤ n ≤ 3·10⁵) — the number of points on the line.

The second line contains n integers x_i ( - 10⁹ ≤ x_i ≤ 10⁹) — the coordinates of the given n points.

Output

　　Print the only integer x — the position of the optimal point on the line. If there are several optimal points print the position of the leftmost one. It is guaranteed that the answer is always the integer.

Example

Input

4
1 2 3 4

Output

2

题意：
　　给出N个点所在数轴的位置，找一个点，使其他点到这个点的距离和最小
思路：
　　找中位数，就可以了

AC代码：

 1 # include <bits/stdc++.h>
 2 using namespace std;
 3 typedef long long int ll;
 4 const int MAX = 3 * 1e5 + 1;
 5 ll a[MAX];
 6 int main()
 7 {
 8     ll n;
 9     scanf("%I64d", &n);
10     ll sum = 0;
11     for(int i = 1; i <= n; i++)
12     {
13         scanf("%I64d", &a[i]);
14         sum += a[i];
15     }
16     
17     sort(a + 1, a + n + 1);
18     if(n % 2)
19         cout << a[n / 2 + 1] << endl;
20     else
21         cout << a[n / 2] << endl;
22     return 0;
23 }