SRM 607 L2 D2：PalindromicSubstringsDiv2，DP

题目：http://community.topcoder.com/stat?c=problem_statement&pm=12967

暴力法会超时，dp[i][j] 表示 子串 [i...j] 是否为回文串。

代码：

#include <algorithm>
#include <iostream>
#include <sstream>

#include <string>
#include <vector>
#include <stack>
#include <deque>
#include <queue>
#include <set>
#include <map>

#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <cmath>
#include <cstring>

#include<ctime>

using namespace std;

#define CHECKTIME() printf("%.2lf\n", (double)clock() / CLOCKS_PER_SEC)

/*************** Program Begin **********************/

bool dp[5000][5001];

class PalindromicSubstringsDiv2 {
public:
int count(vector <string> S1, vector <string> S2) {
memset(dp, 0, sizeof(dp));
int res = 0;
string S;
for (int i = 0; i < S1.size(); i++) {
S += S1[i];
}
for (int i = 0; i < S2.size(); i++) {
S += S2[i];
}
int N = S.size();

for (int i = 0; i < N; i++) {
dp[i][i] = true;
++res;
}
for (int len = 2; len <= N; len++) {
for (int i = 0; i <= N - len; i++) {
if (S[i] == S[i + len - 1]) {
if (len == 2 || dp[i+1][i + len - 2] == true) {
dp[i][i+ len - 1] = true;
++res;
}

}
}
}

return res;
}
};

/************** Program End ************************/