HDU 1503 Advanced Fruits(LCS)

Advanced Fruits

#include <iostream>
#include <string>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <vector>

using namespace std;

#define maxn 1005
int ans[maxn][maxn];
int mark[maxn][maxn];
string s1, s2;

void printLCS(int i,int j) {
    if(i == 0 && j == 0)
        return ;
    if(mark[i][j] == 0) {
        printLCS(i-1,j-1);
        cout << s1[i-1];
    } else if(mark[i][j] == 1) { //根据回溯的位置进行输出
        printLCS(i-1,j);
        cout << s1[i-1];
    } else {
        printLCS(i,j-1);
        cout << s2[j-1];
    }
}

int longestCommonSubsequence(string A, string B) {
    int m = A.size();
    int n = B.size();

    for(int i = 0; i <= m; ++i) {
        ans[i][0] = 0;
        mark[i][0] = 1;//1：用A[i-1]添加
    }

    for(int j = 0; j <= n; ++j) {
        ans[0][j] = 0;
        mark[0][j] = -1;//-1: 用B[j-1]添加
    }

    for(int i = 1; i <= m; ++i) {
        for(int j = 1; j <= n; ++j) {
            if(A[i-1] == B[j-1]) {
                ans[i][j] = ans[i-1][j-1] + 1;
                mark[i][j] = 0;//A[i-1]、B[j-1]都可以添加
            } else  {
                if(ans[i-1][j] > ans[i][j-1]) {
                    ans[i][j] = ans[i-1][j];
                    mark[i][j] = 1;//1：用A[i-1]添加
                } else {
                    ans[i][j] = ans[i][j-1];
                    mark[i][j] = -1;//-1: 用B[j-1]添加
                }
            }
        }
    }

    return ans[m][n];
}

int main() {
    //freopen("data.in","r",stdin);
    ios::sync_with_stdio(false);

    while(cin >> s1 >> s2 ) {
        int res = longestCommonSubsequence(s1, s2);
        printLCS(s1.length(), s2.length());
        cout << endl;
    }

    return 0;
}