【鏈接】
bzoj1037
【解題報告】
定義
轉移方程:
放一個男生:
放一個女生:
所以直接推DP就行了。
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int maxv=305,maxn=155,maxm=21,tt=12345678;
int n,m,K,ans,f[maxv][maxn][maxm][maxm];
int main()
{
freopen("1037.in","r",stdin);
freopen("1037.out","w",stdout);
scanf("%d%d%d",&n,&m,&K); ans=0;
memset(f,0,sizeof(f));
f[0][0][0][0]=1;
for (int i=0; i<n+m; i++)
for (int j=0; j<=min(n,i); j++)
for (int s=0; s<=K; s++)
for (int t=0,x; t<=K; t++)
if (f[i][j][s][t])
{
if (s+1<=K&&j+1<=n) x=max(t-1,0),f[i+1][j+1][s+1][x]=(f[i+1][j+1][s+1][x]+f[i][j][s][t])%tt;
if (t+1<=K&&i+1-j<=m) x=max(s-1,0),f[i+1][j][x][t+1]=(f[i+1][j][x][t+1]+f[i][j][s][t])%tt;
}
for (int i=0; i<=K; i++)
for (int j=0; j<=K; j++)
ans=(ans+f[n+m][n][i][j])%tt;
printf("%d",ans);
return 0;
}