2016秋季练习

来源：lightOJ 1025

区间DP，构造回文串，还是比较简单的，注意longlong

代码：#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int MAXN = 70;
char ch[MAXN];
long long dp[MAXN][MAXN];
int main(){
int T,nc = 1;
scanf("%d",&T);
getchar();
while(T--){
gets(ch);
int n = strlen(ch);
memset(dp,0,sizeof dp);
// for(int i=0;i<n;i++) dp[i][i] = 1;
for(int l=1;l<=n;l++){
// cout<<"len = "<<l<<endl;
for(int i=0;i+l-1<n;i++){
int j = i+l-1;
// cout<<i<<" "<<j<<" ";
dp[i][j] += dp[i+1][j];
dp[i][j] += dp[i][j-1];
if(ch[i] == ch[j]) dp[i][j] ++;
else dp[i][j] -= dp[i+1][j-1];
// cout<<dp[i][j]<<endl;
}
}
printf("Case %d: %lld\n",nc++,dp[0][n-1]);
}

return 0;
}