二叉樹的遞迴與非遞迴遍歷演算法
阿新 • • 發佈:2019-02-11
/*二叉樹的遍歷**/ #include <iostream> #include<string.h> #include<stack> using namespace std; typedef struct node { char data; struct node *lchild,*rchild; }BinTree; typedef struct node1 { BinTree *btnode; bool isFirst; }BTNode; void creatBinTree(char *s,BinTree *&root) //建立二叉樹,s為形如A(B,C(D,E))形式的字串 { int i; bool isRight=false; stack<BinTree*> s1; //存放結點 stack<char> s2; //存放分隔符 BinTree *p,*temp; root->data=s[0]; root->lchild=NULL; root->rchild=NULL; s1.push(root); i=1; while(i<strlen(s)) { if(s[i]=='(') { s2.push(s[i]); isRight=false; } else if(s[i]==',') { isRight=true; } else if(s[i]==')') { s1.pop(); s2.pop(); } else if(isalpha(s[i])) { p=(BinTree *)malloc(sizeof(BinTree)); p->data=s[i]; p->lchild=NULL; p->rchild=NULL; temp=s1.top(); if(isRight==true) { temp->rchild=p; cout<<temp->data<<"的右孩子是"<<s[i]<<endl; } else { temp->lchild=p; cout<<temp->data<<"的左孩子是"<<s[i]<<endl; } if(s[i+1]=='(') s1.push(p); } i++; } } void display(BinTree *root) //顯示樹形結構 { if(root!=NULL) { cout<<root->data; if(root->lchild!=NULL) { cout<<'('; display(root->lchild); } if(root->rchild!=NULL) { cout<<','; display(root->rchild); cout<<')'; } } } void preOrder1(BinTree *root) //遞迴前序遍歷 { if(root!=NULL) { cout<<root->data<<" "; preOrder1(root->lchild); preOrder1(root->rchild); } } void inOrder1(BinTree *root) //遞迴中序遍歷 { if(root!=NULL) { inOrder1(root->lchild); cout<<root->data<<" "; inOrder1(root->rchild); } } void postOrder1(BinTree *root) //遞迴後序遍歷 { if(root!=NULL) { postOrder1(root->lchild); postOrder1(root->rchild); cout<<root->data<<" "; } } void preOrder2(BinTree *root) //非遞迴前序遍歷 { stack<BinTree*> s; BinTree *p=root; while(p!=NULL||!s.empty()) { while(p!=NULL) { cout<<p->data<<" "; s.push(p); p=p->lchild; } if(!s.empty()) { p=s.top(); s.pop(); p=p->rchild; } } } void inOrder2(BinTree *root) //非遞迴中序遍歷 { stack<BinTree*> s; BinTree *p=root; while(p!=NULL||!s.empty()) { while(p!=NULL) { s.push(p); p=p->lchild; } if(!s.empty()) { p=s.top(); cout<<p->data<<" "; s.pop(); p=p->rchild; } } } void postOrder2(BinTree *root) //非遞迴後序遍歷 { stack<BTNode*> s; BinTree *p=root; BTNode *temp; while(p!=NULL||!s.empty()) { while(p!=NULL) //沿左子樹一直往下搜尋,直至出現沒有左子樹的結點 { BTNode *btn=(BTNode *)malloc(sizeof(BTNode)); btn->btnode=p; btn->isFirst=true; s.push(btn); p=p->lchild; } if(!s.empty()) { temp=s.top(); s.pop(); if(temp->isFirst==true) //表示是第一次出現在棧頂 { temp->isFirst=false; s.push(temp); p=temp->btnode->rchild; } else //第二次出現在棧頂 { cout<<temp->btnode->data<<" "; p=NULL; } } } } void postOrder3(BinTree *root) //非遞迴後序遍歷 { stack<BinTree*> s; BinTree *cur; //當前結點 BinTree *pre=NULL; //前一次訪問的結點 s.push(root); while(!s.empty()) { cur=s.top(); if((cur->lchild==NULL&&cur->rchild==NULL)|| (pre!=NULL&&(pre==cur->lchild||pre==cur->rchild))) { cout<<cur->data<<" "; //如果當前結點沒有孩子結點或者孩子節點都已被訪問過 s.pop(); pre=cur; } else { if(cur->rchild!=NULL) s.push(cur->rchild); if(cur->lchild!=NULL) s.push(cur->lchild); } } } int main(int argc, char *argv[]) { char s[100]; while(scanf("%s",s)==1) { BinTree *root=(BinTree *)malloc(sizeof(BinTree)); creatBinTree(s,root); display(root); cout<<endl; preOrder2(root); cout<<endl; inOrder2(root); cout<<endl; postOrder2(root); cout<<endl; postOrder3(root); cout<<endl; } return 0; }