互不攻击的象 (Bishops,UVa 10237)

#include <iostream>
#include <string.h>
#include <string>
#include <fstream>
#include <algorithm>
#include <stdio.h>
#include <vector>
#include <queue>
#include <set>
#include <cmath>
using namespace std;
const double eps = 1e-8;
const double pi=acos(-1.0);
const int INF=0x7fffffff;
unsigned long long uINF = ~0LL;
#define MAXN 1007
#define mod 1000000007
typedef long long LL;

LL d1[33][1000],d2[33][1000];
LL len1[33],len2[33];
int n,k;
void init()
{
    len1[1]=len1[2]=1;
    len2[1]=len2[2]=2;
    for(int i=3;i<=30;i+=2)
    {
        len1[i]=len1[i+1]=len1[i-1]+2;
        len2[i]=len2[i+1]=len2[i-1]+2;
    }
}
//D[i,j] = (Len[i]-j+1)*D[i-1,j-1] + D[i-1,j]
int main()
{
    //freopen("0.in","r",stdin);
    init();
    while(scanf("%d%d",&n,&k),n+k!=0)
    {
        memset(d1,0,sizeof(d1));
        memset(d2,0,sizeof(d2));

        for(int i=0;i<=n;i++)
        {
            d1[i][0]=1;d2[i][0]=1;
        }

        for(int i=1;i<=n;i++)
        for(int j=1;j<=k;j++)
        {
            d1[i][j]=(len1[i]-j+1)*d1[i-1][j-1]+d1[i-1][j];
            if(i!=n)d2[i][j]=(len2[i]-j+1)*d2[i-1][j-1]+d2[i-1][j];
        }

        LL ans=0;
        for(int i=0;i<=k;i++)
        ans+=d1[n][i]*d2[n-1][k-i];
        printf("%lld
",ans);
    }

    return 0;
}

D[i,j] = (Len[i]-j+1)*D[i-1,j-1] + D[i-1,j]
对棋盘染色 跟国际象棋的棋盘一样 分成两部分 旋转45° 后 分别dp
ans=d[n][i]+d[n-1][k-i];