uva 536Tree Recovery

#include <cstdio>#include <iostream>#include <cstring>#include <algorithm>using namespace std;void build(int n, char *s1, char *s2, char *s){    if(n <= 0) return;    int p = strchr(s2, s1[0]) - s2;    build(p, s1+1, s2, s);    build(n-p-1, s1+p+1, s2+p+1, s+p);    s[n-1] = s1[0];}int main(){    char s1[30], s2[30], ans[30];    while(scanf("%s%s", s1, s2) == 2)    {        int n =strlen(s1);        build(n, s1, s2, ans);        ans[n] = '\0';        cout << ans << endl;    }    return 0;}