Hierarchical traversal of Uva-122 tree, pointer solution

Let’s not talk about the topic. There are a lot of them on Baidu, and there are Chinese and English versions. Let’s share the solution of the author of Zishu. I personally think there are many places to learn:

#include<iostream>
#include<cstring>
#include<cstdlib>
#include<cstdio>
using namespace std;
//(11,LL) (7,LLL) (8,R) (5,) (4,L) (13,RL) (2,LLR) (1,RRR) (4,RR) ()
struct node
{
    bool hv; //have value
    int data;
    node *left,*right;
};
node* root;
bool failed=false;
node * newnode ()
{
    node * p;
    p=(node*)malloc(sizeof(node));
    if(p!=NULL)
    {
        p->hv=false;
        p->left=p->right=NULL;
    }
    return p;
}
void addnode(int k,char* c)
{
    node* p=root;
    while(*c)
    {
        if(*c=='L')
        {
            if(p->left==NULL)
                p->left=newnode();
            p=p->left;
        }
        else if(*c=='R')
        {
            if(p->right==NULL)
                p->right=newnode();
            p=p->right;
        }
        else
            break;
        c++;
    }
    if(p->hv==false)
        p->data=k;
    else
        failed=true;
    p->hv=true;  //DON'T FORGET TO SET HV TO TRUE!!!
}
void remove_tree(node* root)
{
    if(root!=NULL)
    {
        remove_tree(root->left);
        remove_tree(root->right);
        free(root);
    }
}

int init()
{
    //return 0: no end-of-input
    //return 1: input ended successfully
    char s[300];
    remove_tree(root);
    root=newnode();
    while(scanf("%s",s) == 1)
    {
        if(strcmp(s,"()")==0)
            return 1;
        int d;
        sscanf(&s[1],"%d",&d);
        addnode(d,strchr(s,',')+1);
    }
    return 0;
}
int bfs()
{
    node* queue[300];
    int front,rear,out[300],t=0;
    queue[front=rear=1]=root;
    while(front<=rear)
    {
        node* p=queue[front];
        if(p->hv==false)
            return 0;
        out[++t]=p->data;
        if(p->left!=NULL)
            queue[++rear]=p->left;
        if(p->right!=NULL)
            queue[++rear]=p->right;
        front++;
    }
    for(int i=1; i<=t; i++)
        cout << out[i] <<" " ;
    cout << endl;
    return 1;
}
intmain()
{
    while(init()==1)
    {
        if(!bfs())
            failed=true;
        if(failed)
            cout << "-1" << endl;
    }
    return 0;
}

The general idea is to use a linked list to simulate the construction of a binary tree.

1. The special usage of the while() loop is used in line 29. The author has seen this usage in python. Today, I am fortunate to see it in C++. I have to say that C++ never ends.

A slicing idea, such as the first set of test data (11, LL), addnode (K=11, *c=“LL)”), if it were me, I would write a char temp; then the for loop assigns values ​​in turn, Encountered ')' break; but a while (*c) using the slicing idea directly wrote all my thoughts.