hdu 4632 Palindrome subsequence（dp）

代码

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;
const int maxn = 1005;
const int mod = 10007;

char str[maxn];
int N, dp[maxn][maxn];

int solve () {
N = strlen(str + 1);
for (int i = 1; i <= N; i++) dp[i][i] = 1;
for (int i = 1; i < N; i++)
if (str[i] == str[i+1]) dp[i][i+1] = 3;
else dp[i][i+1] = 2;

for (int i = N; i; i--) {
for (int j = i + 2; j <= N; j++) {
dp[i][j] = ((dp[i+1][j] + dp[i][j-1] - dp[i+1][j-1]) % mod + mod) % mod;
if (str[i] == str[j])
dp[i][j] = (dp[i][j] + dp[i+1][j-1] + 1) % mod;
}
}
return dp[1]
;
}

int main () {
int cas;
scanf("%d", &cas);
for (int kcas = 1; kcas <= cas; kcas++) {
scanf("%s", str + 1);
printf("Case %d: %d\n", kcas, solve());
}
return 0;
}