UVa 10617 Again Palindromes / 记忆化搜索

删除若干个字母后 剩下的是回文串 求有多少个

记忆化搜索 dp[i][j]表示i j 之间有多少个 其实递推也可以的 long long

#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;}