B. Nauuo and Chess
Topic links: http://codeforces.com/contest/1173/problem/B
topic
Nauuo is a girl who loves playing chess.
One day she invented a game by herself which needs n chess pieces to play on a m×m chessboard. The rows and columns are numbered from 1 to m. We denote a cell on the intersection of the r-th row and c-th column as (r,c)
The game's goal is to place n chess pieces numbered from 1 to n on the chessboard, the i-th piece lies on (ri,ci), while the following rule is satisfied: for all pairs of pieces i and j, |ri−rj|+|ci−cj|≥|i−j|. Here |x| means the absolute value of x.
However, Nauuo discovered that sometimes she couldn't find a solution because the chessboard was too small.
She wants to find the smallest chessboard on which she can put n
pieces according to the rules.
She also wonders how to place the pieces on such a chessboard. Can you help her?
Input
The only line contains a single integer n(1≤n≤1000) — the number of chess pieces for the game.
Output
The first line contains a single integer — the minimum value of m, where m
is the length of sides of the suitable chessboard.
The i-th of the next n lines contains two integers ri and ci (1≤ri,ci≤m) — the coordinates of the i-th chess piece.
If there are multiple answers, print any.
Example
input
2
output
2
1 1
1 2
The meaning of problems
Give you a number, which you put these numbers 1 ~ n in the grid, such that any two numbers a-> b taking the number of cells in the grid is greater than equal to | ab & | value
Output position of each number 1 ~ n
Thinking
Give you a form to find the law
| 1 | 2 | ||
| 3 | 4 | ||
| 5 | 6 | ||
Travel route for the first down then right, the number of steps to the difference between the two numbers are equal
#include<bits/stdc++.h> using namespace std; int main() { int n; cin>>n; cout<<n/2+1<<endl; for(int i=1;i<=n;i++) { cout<<(i+1)/2<<' '<<i/2+1<<endl; } return 0; }