模板 - 最長公共子序列

最長公共子序列

#include <stdio.h>
#include <iostream>
#include <string.h>
#include <algorithm>
using namespace std;

string str;
char s1[1000], s2[1000];
int dp[1000][1000], mark[1000][1000];///數據太大，dp數組變成滾動數組

int LCS()
{
    int i, j, n, m;
    memset(dp,0,sizeof(dp));
    n = strlen(s1);
    m = strlen(s2);
    for(i = 0; i <= n; i++)
        mark[i][0] = 1;
    for(i = 0; i <= m; i++)
        mark[0][i] = -1;
    for(i = 1; i <= n; i++)
    {
        for(j = 1; j <= m; j++)
        {
            if(s1[i-1] == s2[j-1])
            {
                dp[i][j] = dp[i-1][j-1] + 1;
                mark[i][j] = 0;
            }
            else if(dp[i-1][j] >= dp[i][j-1])
            {
                dp[i][j] = dp[i-1][j];
                mark[i][j] = 1;
            }
            else
            {
                dp[i][j] = dp[i][j-1];
                mark[i][j] = -1;
            }
        }
    }
    return dp[n][m];
}

void SameLCS(int i,int j)///mark[i][j] == 1表示s1序列的,mark[i][j] == -1表示s2序列的
{
    if(!i && !j)
        return ;
    if(mark[i][j] == 0)///公共序列
    {
        SameLCS(i-1,j-1);
        str += s1[i-1];
    }
    else if(mark[i][j] == 1)
        SameLCS(i-1,j);
    else
        SameLCS(i,j-1);
}

int main()
{
    while(~scanf("%s %s",s1,s2))
    {
        int ans, len1, len2;
        len1 = strlen(s1);
        len2 = strlen(s2);
        ans = LCS();
        printf("%d\n",ans);
        SameLCS(len1,len2);
        cout << str << endl;
    }
    return 0;
}