Codeforces Educational 38 B. Run For Your Prize

题目描述

You and your friend are participating in a TV show “Run For Your Prize”.

At the start of the show n prizes are located on a straight line. i-th prize is located at position ai. Positions of all prizes are distinct. You start at position 1, your friend — at position 106 (and there is no prize in any of these two positions). You have to work as a team and collect all prizes in minimum possible time, in any order.

You know that it takes exactly 1 second to move from position x to position x + 1 or x - 1, both for you and your friend. You also have trained enough to instantly pick up any prize, if its position is equal to your current position (and the same is true for your friend). Carrying prizes does not affect your speed (or your friend’s speed) at all.

Now you may discuss your strategy with your friend and decide who will pick up each prize. Remember that every prize must be picked up, either by you or by your friend.

What is the minimum number of seconds it will take to pick up all the prizes?

输入

The first line contains one integer n (1 ≤ n ≤ 105) — the number of prizes.

The second line contains n integers a1, a2, …, an (2 ≤ ai ≤ 106 - 1) — the positions of the prizes. No two prizes are located at the same position. Positions are given in ascending order.

输出

Print one integer — the minimum number of seconds it will take to collect all prizes.

样例

input 3 2 3 9 output 8 input 2 2 999995 output 5

题意

前后两个点向中间开始遍历， 问遍历最小时间是多少 一直更新 min(左边消耗时间，右边消耗时间) m i n ( 左 边 消 耗 时 间 ， 右 边 消 耗 时 间 ) 求得最大值

AC代码

#include <bits/stdc++.h> using namespace std; #define LL long long #define CLR(a,b) memset(a,(b),sizeof(a)) const int MAXN = 1e6; const int INF = 0x3f3f3f3f; const LL INFLL = ~0ull>>1; int arr[MAXN], ans; int main() { ios::sync_with_stdio(false),cin.tie(0); int n; cin >> n; for(int i = 0; i < n; i++) { cin >> arr[i]; } for(int i = 0; i < n; i++) { ans = max(ans,min(MAXN-arr[i],arr[i]-1)); } return cout << ans << endl,0; }