P1827 [USACO3.4] 美国血统 American Heritage

#include<bits/stdc++.h>
using namespace std;
string s1,s2;
void dfs(int s,int e,int r){
    int post = s1.find(s2[r]);
    int len1 = post-s;
    int len2 = e-post;
    if(len1){
        dfs(s,post-1,r+1);
    }
    if(len2){
        dfs(post+1,e,r+len1+1);
    }
    cout<<s2[r]; //s1[post]
}
int main(){
	cin>>s2>>s1;
    dfs(0,s1.size()-1,0);
	return 0;
}` ` `