包含前、中、后、层次遍历

#include <bits/stdc++.h>
using namespace std;
queue<int> q;
const int N = 110;
int idx,l[N],r[N];
char w[N];
int root;
void insert(int &root)
{
    char x;
    cin >> x;
    if(x == '#') root = 0;
    else
    {
        root = ++idx,w[root] = x;
        insert(l[root]);
        insert(r[root]);
    }

}
void dfs(int root,int t)
{
    if(!root) return;
    if(t == 0)
        cout << w[root] << " ";
    dfs(l[root],t);
    if(t == 1)
        cout << w[root] << " ";
    dfs(r[root],t);
    if(t == 2)
        cout << w[root] << " ";
}
void Typeshow(int u)
{
    if(u == 0) return;
     q.push(root);
     while(q.size() > 0)
     {
         int bt = q.front();
         cout << w[bt] << " ";
         q.pop();
         if(l[bt]!= 0)
         q.push(l[bt]);
         if(r[bt]!= 0)
         q.push(r[bt]);
     }
}
int main()
{
    insert(root);
    for(int i = 0; i < 3; i++)
    {

        dfs(root,i);
        cout <<endl;
    }
    Typeshow(root);
}
//输入样例
//abc##d##e#f##
//输出样例
//pre_order:a b c d e f
//mid_order:c b d a e f
//post_order:c d b f e a
//quene_order:a b e c d f