一.基本概念
https://www.jianshu.com/p/bf73c8d50dc2 的3.8之前
二.基础代码实施
1.建树
1 Tree *CreatTree(Tree *root){
2 int c;
3 c = getchar();
4 if(c == '#') root = NULL;//是特殊字符则没有叶子节点
5 else {//从左至右建树 6 root = new Tree;
7 root->date = c;
8 root->left = CreatTree(root->left);
9 root->right = CreatTree(root->right);
10 }
11 return root;
12 }
如：构造下列二叉树
那么我们的输入应该是: ABDG##H###CE#I##F##
解析:
从A->G:未遇见特殊字符'#',依次建立左子树.
G->H:G后读入特殊字符'#',则G左孩子为空;
继续读入下一个字符;
依然是'#',则G右孩子为空.
此时G左右孩子已输入,返回上一层D.
读入字符'H'写入D右孩子.
其他的以此类推即可
2.遍历
（1）前序遍历
双亲->左->右
1 void PreOrder(Tree *root) { 2 if(root == NULL) return; 3 putchar(root->date);//输出等操作 4 PreOrder(root->left); 5 PreOrder(root->right); 6 }
依照上图前序遍历结果:
A B D G H C E I F
（2）中序遍历
左->双亲->右
1 void InOrder(Tree *root) { 2 if(root == NULL) return; 3 InOrder(root->left); 4 putchar(root->date); 5 InOrder(root->right); 6 }
中序遍历结果:
G D H B A E I C F
（3）后序遍历
左->右->双亲
1 void PostOrder(Tree *root) { 2 if(root == NULL) return; 3 PostOrder(root->left); 4 PostOrder(root->right); 5 putchar(root->date); 6 }
后序遍历结果:
G H D B I E F C A
3.销毁
1 void DesTree(Tree *root) 2 { 3 if(root == NULL) return ; 4 DesTree(root->left); 5 DesTree(root->right); 6 free(root); //从最右依次free至根节点 7 }
完整代码
1 #include <bits/stdc++.h> 2 3 using namespace std; 4 #define ll long long 5 #define pi acos(-1) 6 #define mod 1000000007 7 8 typedef struct TREE{ 9 char date; 10 struct TREE *left, *right; 11 }Tree; 12 13 Tree *CreatTree(Tree*); 14 void PreOrder(Tree*); 15 void InOrder(Tree*); 16 void PostOrder(Tree*); 17 void DesTree(Tree *root); 18 19 int main() { 20 Tree *root = NULL; 21 root = CreatTree(root); 22 PreOrder(root); 23 printf(" "); 24 InOrder(root); 25 printf(" "); 26 PostOrder(root); 27 DesTree(root); 28 return 0; 29 } 30 //建树 31 Tree *CreatTree(Tree *root){ 32 int c; 33 c = getchar(); 34 if(c == '#') root = NULL; 35 else { 36 root = new Tree; 37 root->date = c; 38 root->left = CreatTree(root->left); 39 root->right = CreatTree(root->right); 40 } 41 return root; 42 } 43 //前序 44 void PreOrder(Tree *root) { 45 if(root == NULL) return; 46 putchar(root->date); 47 PreOrder(root->left); 48 PreOrder(root->right); 49 } 50 //中序 51 void InOrder(Tree *root) { 52 if(root == NULL) return; 53 InOrder(root->left); 54 putchar(root->date); 55 InOrder(root->right); 56 } 57 //后序 58 void PostOrder(Tree *root) { 59 if(root == NULL) return; 60 PostOrder(root->left); 61 PostOrder(root->right); 62 putchar(root->date); 63 }
63 //销毁 64 void DesTree(Tree *root) 65 { 66 if(root == NULL) return ; 67 DesTree(root->left); 68 DesTree(root->right); 69 free(root); 70 } 71 72 //for(int i = 0; i < n; i++)
参考博文 https://blog.csdn.net/bestsort/article/details/78784419
https://www.jianshu.com/p/bf73c8d50dc2