Codeforces Round 593 (Div. 2)
D
Alice and the Doll
Codeforces
2300
原题
← CE →
翻译中…

Alice got a new doll these days. It can even walk!

翻译中…

Alice has built a maze for the doll and wants to test it. The maze is a grid with $n$ rows and $m$ columns. There are $k$ obstacles, the $i$-th of them is on the cell $(x_i, y_i)$, which means the cell in the intersection of the $x_i$-th row and the $y_i$-th column.

翻译中…

However, the doll is clumsy in some ways. It can only walk straight or turn right at most once in the same cell (including the start cell). It cannot get into a cell with an obstacle or get out of the maze.

翻译中…

More formally, there exist $4$ directions, in which the doll can look:

翻译中…
  1. The doll looks in the direction along the row from the first cell to the last. While moving looking in this direction the doll will move from the cell $(x, y)$ into the cell $(x, y + 1)$;
  2. The doll looks in the direction along the column from the first cell to the last. While moving looking in this direction the doll will move from the cell $(x, y)$ into the cell $(x + 1, y)$;
  3. The doll looks in the direction along the row from the last cell to first. While moving looking in this direction the doll will move from the cell $(x, y)$ into the cell $(x, y - 1)$;
  4. The doll looks in the direction along the column from the last cell to the first. While moving looking in this direction the doll will move from the cell $(x, y)$ into the cell $(x - 1, y)$.
翻译中…

.

翻译中…

Standing in some cell the doll can move into the cell in the direction it looks or it can turn right once. Turning right once, the doll switches it's direction by the following rules: $1 \to 2$, $2 \to 3$, $3 \to 4$, $4 \to 1$. Standing in one cell, the doll can make at most one turn right.

翻译中…

Now Alice is controlling the doll's moves. She puts the doll in of the cell $(1, 1)$ (the upper-left cell of the maze). Initially, the doll looks to the direction $1$, so along the row from the first cell to the last. She wants to let the doll walk across all the cells without obstacles exactly once and end in any place. Can it be achieved?

翻译中…

Input

翻译中…

The first line contains three integers $n$, $m$ and $k$, separated by spaces ($1 \leq n,m \leq 10^5, 0 \leq k \leq 10^5$) — the size of the maze and the number of obstacles.

翻译中…

Next $k$ lines describes the obstacles, the $i$-th line contains two integer numbers $x_i$ and $y_i$, separated by spaces ($1 \leq x_i \leq n,1 \leq y_i \leq m$), which describes the position of the $i$-th obstacle.

翻译中…

It is guaranteed that no two obstacles are in the same cell and no obstacle is in cell $(1, 1)$.

翻译中…

Output

翻译中…

Print 'Yes' (without quotes) if the doll can walk across all the cells without obstacles exactly once by the rules, described in the statement.

翻译中…

If it is impossible to walk across the maze by these rules print 'No' (without quotes).

翻译中…

Note

翻译中…

Here is the picture of maze described in the first example:

翻译中…

image

翻译中…

In the first example, the doll can walk in this way:

翻译中…
  • The doll is in the cell $(1, 1)$, looks to the direction $1$. Move straight;
  • The doll is in the cell $(1, 2)$, looks to the direction $1$. Move straight;
  • The doll is in the cell $(1, 3)$, looks to the direction $1$. Turn right;
  • The doll is in the cell $(1, 3)$, looks to the direction $2$. Move straight;
  • The doll is in the cell $(2, 3)$, looks to the direction $2$. Move straight;
  • The doll is in the cell $(3, 3)$, looks to the direction $2$. Turn right;
  • The doll is in the cell $(3, 3)$, looks to the direction $3$. Move straight;
  • The doll is in the cell $(3, 2)$, looks to the direction $3$. Move straight;
  • The doll is in the cell $(3, 1)$, looks to the direction $3$. The goal is achieved, all cells of the maze without obstacles passed exactly once.
翻译中…

样例

Input #1
3 3 2
2 2
2 1
Output #1
Yes
InputCopy OutputCopy
Input #2
3 3 2
3 1
2 2
Output #2
No
InputCopy OutputCopy
Input #3
3 3 8
1 2
1 3
2 1
2 2
2 3
3 1
3 2
3 3
Output #3
Yes
InputCopy OutputCopy
题目信息
题号
1236D
时间限制
1 s
内存限制
256 MB
标签
暴力
数据结构
贪心
模拟

题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。