《入門經典》2

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <queue>
#include <vector>
#define maxn 20


struct node
{
    int value;
    bool have_value;
    node *left,*right;
    node():value(0),have_value(false),left(NULL),right(NULL){}
};


using namespace std;


char s[maxn];
node *root;
bool failed;

node nodes[256];
queue<node*>pool;

void minit()
{
    int i;
    for(i=0;i<256;++i)
        pool.push(&nodes[i]);
}



node*newnode()
{
    node *a = pool.front();
    pool.pop();
    a -> left = a -> right = 0;
    a -> have_value = false;
    return a;
}


void addnode(int value,char *s)
{
    int i=0,n=strlen(s);
    node *u = root;
    for(;i<n;++i)
    {
        if(s[i] == 'L')
        {
            if(u -> left == NULL)
                u -> left = newnode();
            u = u->left;
        }
        if(s[i] == 'R')
        {
            if(u -> right == NULL)
                u -> right = newnode();
            u = u->right;
        }
    }
    if(u -> have_value) failed = true;
    u -> value = value;
    u -> have_value = true;
}


bool read_input()
{
    failed = false;
    root = newnode();
    for(;;)
    {
        if(scanf("%s",s)!=1)
            return false;
        if(!strcmp(s,"()"))
            break;
        int v;
        sscanf(&s[1],"%d",&v);
        addnode(v,strchr(s,',')+1);
    }
    return true;
}


void pre_dfs(vector<int> &pre_ans,node *u)		//先序
{
    pre_ans.push_back(u -> value);
    if(u -> left != NULL)
        pre_dfs(pre_ans,u -> left);
    if(u -> right != NULL)
        pre_dfs(pre_ans,u -> right);
}

void in_dfs(vector<int> &in_ans,node *u)		//中序
{
    if(u -> left != NULL)
        in_dfs(in_ans,u -> left);
    in_ans.push_back(u -> value);
    if(u -> right != NULL)
        in_dfs(in_ans,u -> right);
}

void post_dfs(vector<int> &post_ans,node *u)		後序
{
    if(u -> left != NULL)
        post_dfs(post_ans,u -> left);
    if(u -> right != NULL)
        post_dfs(post_ans,u -> right);
    post_ans.push_back(u -> value);

}
int main()
{
    minit();
    vector<int> pre_ans;
    pre_ans.clear();
    vector<int> in_ans;
    in_ans.clear();
    vector<int> post_ans;
    post_ans.clear();
    read_input();

    pre_dfs(pre_ans,root);
    in_dfs(in_ans,root);
    post_dfs(post_ans,root);

    size_t i;
    for(i=0;i<pre_ans.size();++i)
        printf("%d ",pre_ans[i]);
    printf("\n");

    for(i=0;i<in_ans.size();++i)
        printf("%d ",in_ans[i]);
    printf("\n");

    for(i=0;i<post_ans.size();++i)
        printf("%d ",post_ans[i]);
    printf("\n");
    return 0;
}

二叉樹 DFS 先序 中序 後序