AtCoder Grand Contest 021C-Tiling

C - Tiling

Time limit : 2sec / Memory limit : 256MB

Score : 900 points

Problem Statement

Takahashi has an N×M grid,
with N horizontal rows and M vertical
columns. Determine if we can place A 1×2 tiles
(1 vertical, 2 horizontal)
and B 2×1 tiles
(2vertical, 1 horizontal)
satisfying the following conditions, and construct one arrangement of the tiles if it is possible:
All the tiles must be placed on the grid.
Tiles must not stick out of the grid, and no two different tiles may intersect.
Neither the grid nor the tiles may be rotated.
Every tile completely covers exactly two squares.

Constraints

1≤N,M≤1000
0≤A,B≤500000
N, M, A and B are
integers.

Input

Input is given from Standard Input in the following format:

N M A B

Output

If it is impossible to place all the tiles, print 

NO

.
Otherwise, print the following:

YES
c11…c1M
:
cN1…cNM

Here, cij must
be one of the following characters: 

.

, 

<

, 

>

, 

^

 and 

v

.
Represent an arrangement by using each of these characters as follows:
When cij is 

.

,
it indicates that the square at the i-th row and j-th
column is empty;
When cij is 

<

,
it indicates that the square at the i-th row and j-th
column is covered by the left half of a 1×2 tile;
When cij is 

>

,
it indicates that the square at the i-th row and j-th
column is covered by the right half of a 1×2 tile;
When cij is 

^

,
it indicates that the square at the i-th row and j-th
column is covered by the top half of a 2×1 tile;
When cij is 

v

,
it indicates that the square at the i-th row and j-th
column is covered by the bottom half of a 2×1 tile.

Sample Input 1

Copy

3 4 4 2

Sample Output 1

Copy

YES
<><>
^<>^
v<>v

This is one example of a way to place four 1×2 tiles
and three 2×1 tiles on a 3×4 grid.

Sample Input 2

Copy

4 5 5 3

Sample Output 2

Copy

YES
<>..^
^.<>v
v<>.^
<><>v

Sample Input 3

Copy

7 9 20 20

Sample Output 3

Copy

NO

Submit
       模拟题坑死人！！！
       题解

Code：#include<iostream>
#include<cmath>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<cstdlib>
#define N 1005
using namespace std;
char ans

;
inline int read()
{
int x=0,f=1;char s=getchar();
while(s<'0'||s>'9'){if(s=='-')f=-1;s=getchar();}
while(s<='9'&&s>='0'){x=x*10+s-'0';s=getchar();}
return x*f;
}
int main()
{
int n=read(),m=read(),a=read(),b=read();
memset(ans,'.',sizeof(ans));
for(int i=1;i<=n;i++)ans[i][m+1]='\0';
if(n&1)
{
int j=1;
while(a&&j+1<=m)
{
ans
[j]='<';
ans
[j+1]='>';
j+=2;
a--;
}
}
if(m&1)
{
int i=n;
while(b&&i>1)
{
ans[i-1][m]='^';
ans[i][m]='v';
i-=2;
b--;
}
}
for(int i=n/2;i>=1;i--)
for(int j=1;j<=m/2;j++)
{
int x=i*2-1,y=j*2-1;
if(n%2==1&&m%2==1&&a==1&&b==1&&i==1&&j==m/2)
{
ans[x][y]='^';
ans[x+1][y]='v';
b--;
ans[x][y+1]='<';
ans[x][y+2]='>';
a--;
}
if(a&&b<2)
{
ans[x][y]='<';
ans[x][y+1]='>';
a--;
if(a)
{
ans[x+1][y]='<';
ans[x+1][y+1]='>';
a--;
}
}else if(b)
{
ans[x][y]='^';
ans[x+1][y]='v';
b--;
if(b)
{
ans[x][y+1]='^';
ans[x+1][y+1]='v';
b--;
}
}
}
if(a||b)puts("NO");else
{
puts("YES");
for(int i=1;i<=n;i++)puts(ans[i]+1);
}
return 0;
}