POJ 1159 Palindrome

L(longest)C(common)S(sequence)经典问题，要用滚动数组，不然会爆内存。

#include <iostream>#include <string>#include <cstring>#include <algorithm>using namespace std;int dp[2][5005];int main() {    string s1, s2;    int n;    while (cin >> n) {        cin >> s1;        s2 = s1;        reverse(s2.begin(), s2.end());        memset(dp, 0, sizeof(dp));        for (int i = 1; i <= n; i++) {            for (int j = 1; j <= n; j++) {  //  notice the order                dp[i % 2][j] = dp[(i - 1) % 2][j] > dp[i % 2][j - 1] ? dp[(i - 1) % 2][j] : dp[i % 2][j - 1];                if (s1[i - 1] == s2[j - 1]) {                    int temp = dp[(i - 1) % 2][j - 1] + 1;                    dp[i % 2][j] = dp[i % 2][j] > temp ? dp[i % 2][j] : temp;                }            }        }        cout << n - dp[n % 2][n] << "\n";    }    return 0;}