【算法】最长公共子序列-dp

#include<iostream>
#include<algorithm>
using namespace std;
const int maxn =1e3+5;
char x[maxn],y[maxn];
int c[maxn][maxn];
int ans[maxn][maxn];

int getMaxLen(int n1,int n2)
{
    for(int i =1;i<=n1;++i) c[i][0]=0;
    for(int i =1;i<=n2;++i) c[0][i]=0;

    for(int i =1 ;i<=n1;++i)
    {
        for(int j=1;j<=n2;++j)
        {
            if(x[i]==y[j])
            {
                c[i][j]=c[i-1][j-1]+1;
                ans[i][j]=1;
            }
            else
            {
                if(c[i-1][j]>=c[i][j-1])
                {
                    c[i][j]=c[i-1][j];
                    ans[i][j]=2;
                }
                else
                {
                    c[i][j]=c[i][j-1];
                    ans[i][j]=3;
                }
            }
        }
    }
    return c[n1][n2];
}

void getAns(int i,int j)
{
    if(i==0||j==0) return ;

    if(ans[i][j]==1)
    {
        getAns(i-1,j-1);
        cout<<x[i];
    }
    else if(ans[i][j]==2) 
    {
        getAns(i-1,j);
    }
    else 
    {
        getAns(i,j-1);
    }
    
}
int main()
{
    int n1,n2;
    cin>>n1>>n2;
    for(int i =1 ;i<=n1;++i) cin>>x[i];
    for(int i =1 ;i<=n2;++i) cin>>y[i];

    cout<<getMaxLen(n1,n2)<<endl;
    getAns(n1,n2);

}