贴个baka爷的代码留念。。
数据出的有问题，输入的字符串长度不超过1000
#include #include #include #include #include #include #include #include #include #include #define inf 0x3f3f3f3f #define Inf 0x3FFFFFFFFFFFFFFFLL #define eps 1e-9 #define pi acos(-1.0) using namespace std; typedef long long ll; const int maxn=1000+2; const int mod=1000000007; int dp[maxn][maxn]; char str[maxn<<1]; int main() { //freopen(in.txt,r,stdin); //freopen(out.txt,w,stdout); int t,n; scanf(%d,&t); while(t--) { scanf(%d,&n); memset(dp,0,sizeof(dp)); scanf(%s,str+1); dp[0][0]=1; int k; for(int i=0;i<=n;++i) for(int j=0;j<=n;++j) { if(!dp[i][j]) continue; k=i+j+1; if((i&1)&&(j&1)) { if(str[k]=='B') { dp[i][j+1]+=dp[i][j]; dp[i+1][j]+=dp[i][j]; if(dp[i][j+1]>=mod) dp[i][j+1]-=mod; if(dp[i+1][j]>=mod) dp[i+1][j]-=mod; } } else if(i&1) { if(str[k]=='W') { dp[i][j+1]+=dp[i][j]; if(dp[i][j+1]>=mod) dp[i][j+1]-=mod; } else { dp[i+1][j]+=dp[i][j]; if(dp[i+1][j]>=mod) dp[i+1][j]-=mod; } } else if(j&1) { if(str[k]=='W') { dp[i+1][j]+=dp[i][j]; if(dp[i+1][j]>=mod) dp[i+1][j]-=mod; } else { dp[i][j+1]+=dp[i][j]; if(dp[i][j+1]>=mod) dp[i][j+1]-=mod; } } else { if(str[k]=='W') { dp[i][j+1]+=dp[i][j]; dp[i+1][j]+=dp[i][j]; if(dp[i][j+1]>=mod) dp[i][j+1]-=mod; if(dp[i+1][j]>=mod) dp[i+1][j]-=mod; } } } int ans=dp[n][n]; printf(%d ,ans); } return 0; }