American Heritage usaco

基础题，主要思路是找到根，然后分别递归即可；

 #include<iostream>
 #include<cstring>
 #include<string>
 #include<cstdio>
 #include<cstdlib>
 using namespace std;
 char s[],t[];
 int n;
 void dfs(int x,int y,int a,int b){
     int k;
     for(int i=a;i<=b;i++)if(s[i]==t[x]){k=i;break;}
     if(k!=a)dfs(x+,x+k-a,a,k-);
     if(k!=b)dfs(x+k-a+,y,k+,b);
     cout<<t[x];
 }
 void work(){
     scanf("%s%s",s,t);
     n=strlen(s);
     dfs(,n-,,n-);
 }
 int main(){
     freopen("1.in","r",stdin);
     freopen("1.out","w",stdout);
     work();
 }