就是求最长公共子序列。

###Code

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//By Brickgao
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <cstdlib>
#include <algorithm>
#include <vector>
using namespace std;
#define out(v) cerr << #v << ": " << (v) << endl
#define SZ(v) ((int)(v).size())
const int maxint = -1u>>1;
template <class T> bool get_max(T& a, const T &b) {return b > a? a = b, 1: 0;}
template <class T> bool get_min(T& a, const T &b) {return b < a? a = b, 1: 0;}

char a[1100], b[1100];
int c[1100][1100];
int la, lb;

int main() {
    while(gets(a) && gets(b)) {
        la = strlen(a);
        lb = strlen(b);
        memset(c, 0, sizeof(c));
        for(int i = 0; i < la; i ++) {
            for(int j = 0; j < lb; j ++) {
                if(a[i] == b[j]) {
                    c[i + 1][j + 1] = c[i][j] + 1; 
                }
                else {
                    c[i + 1][j + 1] = max(c[i][j + 1], c[i + 1][j]); 
                }
            }
        }
        cout << c[la][lb] << endl;
    }
    return 0;
}