UVa 10617 Again Palindromes / 记忆化搜索

#include <stdio.h>
#include <string.h>
long long dp[70][70];
char a[70];
long long n;

long long dfs(long long l,long long r)
{
if(l > r)
return 0;
if(l == r)
return 1;
if(dp[l][r] != -1)
return dp[l][r];
long long ret = 0;
if(a[l] == a[r])
{
ret = dfs(l+1,r) + dfs(l,r-1) + 1;
//ret = dfs(l+1,r) + dfs(l,r-1) - dfs(l+1,r-1)+ dfs(l+1,r-1) + 1;
}
else
{
ret = dfs(l+1,r) + dfs(l,r-1) - dfs(l+1,r-1);
}
dp[l][r] = ret;
return ret;
}
int main()
{
long long t;
scanf("%lld",&t);
while(t--)
{
scanf("%s",a+1);
n = strlen(a+1);
memset(dp,-1,sizeof(dp));
printf("%lld\n",dfs(1,n));
}
return 0;
}