中序遍历树（不一定是二叉树）_中序遍历升序一定是二叉搜索树吗

dfs(father)
    for son in father
        if(not visited)
            dfs(son)
        if(is the first son)
            add(father)
    if father have no son
    add father

#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <algorithm>
#include <cstdlib>
#include <queue>
const int maxn = 1000005;
using namespace std;
typedef long long ll;
const int INF = 0x3f3f3f3f;
#define mem(a,x) memset(a,x,sizeof a)
char s[110];
vector<int>G[110];
string tmp;
int vis[110];
void traverse(int x){
    int isfirst =0;
    for(int i=0;i<G[x].size();i++){
        int nt = G[x][i];
        if(!vis[nt]){
            isfirst ++;
            vis[nt] = true;
            traverse(nt);
            if(isfirst == 1){
                tmp += s[x];
            }
        }
    }
    if(!isfirst)
        tmp += s[x];
}
int main(){
    int n;
    while(scanf("%d",&n) !=EOF){
        scanf("%s",s);
        for(int i=0;i<=n;i++) G[i].clear();
        for(int i=0;i<n-1;i++){
            int a,b;scanf("%d%d",&a,&b);
            G[a].push_back(b);
            G[b].push_back(a);
        }
        vector<string>vt;
        for(int i=0;i<n;i++){
            tmp = "";
            mem(vis,0);
            vis[i] = true;
            traverse(i);
            vt.push_back(tmp);
        }
        sort(vt.begin(),vt.end());
        cout<<vt[0]<<endl;
    }
    return 0;
}