终于过了，原来我没有初始化F[i][0]和F[0][j]
> /*author by gamy*/
> #include<iostream>
> #include<string>
> #include<map>
> #include<deque>
> #include<vector>
> #include<cmath>
> #include<algorithm>
> using namespace std;
> #define N 203
> 
> char A[N],B[N],C[2*N];
> 
> int main()
> {
> 	int ca,k;
> 	cin>>ca;
> 	for(k=1;k<=ca;k++)
> 	{
> 		cin>>A>>B>>C;
> 		cout<<"Data set "<<k<<": ";
> 		int i,j;
> 		bool F[N][N];
> 		F[1][0]=(A[0]==C[0]);
> 		F[0][1]=(B[0]==C[0]);
> 		for(i=1;i<=(int)strlen(A);i++)
> 		{
> 			for(j=1;j<=(int)strlen(B);j++)
> 			{
> 				F[i][j]=F[i][j-1]&&(B[j-1]==C[i+j-1])||F[i-1][j]&&(A[i-1]==C[i+j-1]);
> 			}
> 		}
> 		if(F[(int)strlen(A)][(int)strlen(B)])
> 			cout<<"yes\n";
> 		else cout<<"no\n";
> 	}
> }