Tree

Tree.cpp

#include <iostream>
#include <cstring>
using namespace std;

char pre[100] = "zWbTghHV3oPp8LFGuAfn01rmwxJ7eiQYZ25vKqk9yCBNDU4lcMIEaOj6SRXsdt";        //前序序列
char mid[100] = "TbHVh3ogPWFLuAfGrm1xJ7we0iQYnZ8Kvqk9y5CNBD24UlcpIEMaj6SROXsdzt";        //中序序列
char post[100] = "TVHo3hPgbFfAumr7Jxew1YQi0ZnGLKy9kqvNDBC54clU28EIRS6jdsXOaMpWtz";        //后序序列

typedef struct _Node
{
    char v;
    struct _Node *left;
    struct _Node *right;
    int height;
}Node, *PNode;

void PostTravelTree(PNode pn, int height);        //树的后序递归遍历
void PreTravelTree(PNode pn, int height);        //树的前序递归遍历
void PreMidCreateTree(PNode &pn, int i, int j, int len);        //利用前序中序序列创建树
void PostMidCreateTree(PNode &pn, int i, int j, int len);        //利用后序中序序列创建树
int Position(char c);                //确定c在中序序列mid中的下标,假设树的各个节点的值各不相同


int main() 
{ 
    PNode root1 = NULL, root2= NULL;

    PreMidCreateTree(root1, 0, 0, strlen(mid));
    PostTravelTree(root1, 0); cout<<endl; cout<<endl; cout<<endl;    
    PostMidCreateTree(root2, strlen(post)-1, 0, strlen(mid));
    PreTravelTree(root2, 0); cout<<endl;    

    return 0;
}


int Position(char c)
{
    return strchr(mid,c)-mid;
}


/*  利用前序中序序列创建树,参考了http://hi.baidu.com/sulipol/blog/item/f01a20011dcce31a738b6524.html
 *的实现,代码十分简洁,竟然只有短短的"令人发指"的8行,递归实在太彪悍了!!!!!!!!!!!!!!!!!!!!!
 *        i: 子树的前序序列字符串的首字符在pre[]中的下标
 *        j: 子树的中序序列字符串的首字符在mid[]中的下标
 *      len: 子树的字符串序列的长度
 */
void PreMidCreateTree(PNode &pn, int i, int j, int len)
{
    if(len <= 0)
        return;
    
    pn = new Node;
    pn->v = pre[i];

    int m = Position(pre[i]);
    PreMidCreateTree(pn->left, i+1, j, m-j);            //m-j为左子树字符串长度
    PreMidCreateTree(pn->right, i+(m-j)+1, m+1, len-1-(m-j));    //len-1-(m-j)为右子树字符串长度
}


/*  利用后序中序序列创建树
 *        i: 子树的后序序列字符串的尾字符在post[]中的下标
 *        j: 子树的中序序列字符串的首字符在mid[]中的下标
 *      len: 子树的字符串序列的长度
 */
void PostMidCreateTree(PNode &pn, int i, int j, int len)
{
    if(len <= 0)
        return;

    pn = new Node;
    pn->v = post[i];
    int m = Position(post[i]);
    PostMidCreateTree(pn->left, i-1-(len-1-(m-j)), j, m-j);//注意参数:m-j左子树的长度,len-1-(m-j)右子树的长度
    PostMidCreateTree(pn->right, i-1, m+1, len-1-(m-j));
}


void PostTravelTree(PNode pn, int height)        //后序递归遍历
{
    if(pn)
    {   
        // printf("%d\n", height);

        PostTravelTree(pn->left, height+1);    
        PostTravelTree(pn->right, height+1);
        cout<<height<<" "<<pn->v<<"\n ";
    }
}


void PreTravelTree(PNode pn, int height)        //前序递归遍历
{
    if(pn)
    {
        // pn->height = height;
        cout<<height<<" "<<pn->v<<"\n ";
        PreTravelTree(pn->left, height+1);    
        PreTravelTree(pn->right, height+1);
    }
}