poj 1923 dp（Fourier's Lines）

#include <cstdio>
#include <cstring>
int dp[105][10005];
int n,m,c=1;
int out(int y,int x){
return y<0 || (y>x*(x-1)/2) || (y>0&&y<x-1);
}
int test(int x,int y){
int i;
if(out(y,x))
return 0;
if(!y)
return 1;
if(dp[x][y] != -1)
return dp[x][y];
for(i = 1;i<=x;i++){
dp[x][y] = test(x-i, y-i*(x-i));
if(dp[x][y])
return 1;
}
return 0;
}
int main(){
memset(dp, -1, sizeof(dp));
while(scanf("%d %d",&n,&m) && (n+m)){
printf("Case %d: %d ",c++,n);
if(test(n,m))
printf("lines with exactly %d crossings can cut the plane into %d pieces at most.\n",m,n+m+1);
else
printf("lines cannot make exactly %d crossings.\n",m);
}
return 0;
}