算法学习 - 表达树的建立(后缀表达式法),树的先序遍历,中序遍历,后序遍历(非递归)
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表达树就是依据后缀表达式来建立一个二叉树。
这个二叉树的每一个叶子节点就是数。真祖先都是操作符。
通过栈来建立的,所以这里也会有非常多栈的操作。
树的先序遍历。中序遍历。后序遍历的概念我就不讲了,不会的自行百度,不然也看不懂我的代码。
以下是代码:
// // main.cpp // expressionTree // // Created by Alps on 14-7-29. // Copyright (c) 2014年 chen. All rights reserved. // #include <iostream> #define ElementType char using namespace std; struct Tree; typedef Tree* TreeNode; struct Node; typedef Node* PtrToNode; typedef PtrToNode Stack; struct Tree{ ElementType element; TreeNode left; TreeNode right; }; struct Node{ TreeNode rootNode; Stack Next; }; /****************** Stack operate ****************/ Stack createStack(void){ Stack S = (Stack)malloc(sizeof(Stack)); S->Next = NULL; return S; } int isEmptyStack(Stack S){ return S->Next == NULL; } void Push(TreeNode T, Stack S){ Stack SNode = (Stack)malloc(sizeof(Node)); SNode->rootNode = NULL; SNode->Next = NULL; SNode->rootNode = T; SNode->Next = S->Next; S->Next = SNode; } TreeNode Top(Stack S){ if (!isEmptyStack(S)) { return S->Next->rootNode; }else{ // printf("stack is empty, can‘t get top element!\n"); return NULL; } } void Pop(Stack S){ if (!isEmptyStack(S)) { Stack tmp = S->Next; S->Next = tmp->Next; free(tmp); tmp = NULL; }else{ printf("stack is empty, can‘t pop the stack!\n"); exit(1); } } Stack switchStack(Stack S){ Stack tmp = (Stack)malloc(sizeof(Node)); Stack switchTmp = S->Next; while (switchTmp != NULL) { Push(switchTmp->rootNode, tmp); switchTmp = switchTmp->Next; } return tmp; } int findStack(TreeNode T, Stack S){ Stack tmp = S->Next; while (tmp != NULL) { if (tmp->rootNode == T) { return 1; } tmp = tmp->Next; } return 0; } void PrintStack(Stack S){ if (S == NULL) { printf("please create stack first!\n"); exit(1); } Stack tmp = S->Next; while (tmp != NULL) { ElementType X = tmp->rootNode->element; printf("%c ",X); tmp = tmp->Next; } printf("\n"); } /****************** Tree operate ****************/ TreeNode createNode(ElementType X){ TreeNode expressionTree = (TreeNode)malloc(sizeof(Tree)); expressionTree->element = X; expressionTree->left = NULL; expressionTree->right = NULL; return expressionTree; } TreeNode createTree(ElementType A[], int length, Stack S){ int i = 0; TreeNode tmpNode; for (i = 0; i < length; i++) { tmpNode = createNode(A[i]); if (tmpNode->element == ‘+‘ || tmpNode->element == ‘-‘ || tmpNode->element == ‘*‘ || tmpNode->element == ‘/‘) { tmpNode->right = Top(S); Pop(S); tmpNode->left = Top(S); Pop(S); Push(tmpNode, S); }else{ Push(tmpNode, S); } } return S->Next->rootNode; } int PushTreeNode(TreeNode T, Stack S){ if (T == NULL) { return 0; }else{ Push(T, S); PushTreeNode(T->left, S); PushTreeNode(T->right, S); } return 0; } void PreorderPrint(TreeNode T){ Stack S = createStack(); if (T == NULL) { printf("empty tree\n"); exit(1); } PushTreeNode(T, S); S = switchStack(S); PrintStack(S); } void inOrder(TreeNode T){ Stack S = createStack(); TreeNode tmpTree; if (T == NULL) { printf("empty tree\n"); exit(1); } while (T) { Push(T, S); T = T->left; if (T == NULL) { while (1) { tmpTree = Top(S); if (tmpTree == NULL) { break; } printf("%c ",tmpTree->element); if (tmpTree->right != NULL) { T = tmpTree->right; Pop(S); break; }else{ Pop(S); } } } } printf("\n"); } void afterPreorder(TreeNode T){ Stack S = createStack(); TreeNode tmpTree; Stack saveS = createStack(); if (T == NULL) { printf("empty tree\n"); exit(1); } while (T) { Push(T, S); T = T->left; if (T == NULL) { while (1) { tmpTree = Top(S); if (tmpTree == NULL) { break; } if (tmpTree->right != NULL) { if (findStack(tmpTree, saveS)) { printf("%c ",tmpTree->element); Pop(S); continue; } Push(tmpTree, saveS); T = tmpTree->right; break; }else{ printf("%c ",tmpTree->element); Pop(S); } } } } printf("\n"); } /****************** Main ****************/ int main(int argc, const char * argv[]) { char A[] = {‘a‘,‘b‘,‘+‘,‘c‘,‘d‘,‘e‘,‘+‘,‘*‘,‘*‘}; Stack S = createStack(); int length = sizeof(A)/sizeof(char); TreeNode T = createTree(A, length, S); // printf("%lu\n",sizeof(Node)); printf("create Tree success!\n"); PreorderPrint(T); inOrder(T); afterPreorder(T); return 0; }
代码就是这些~~不懂的留言评论好了~
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