1 #include<iostream> 2 #include<stack> 3 #include<queue> 4 using namespace std; 5 typedef struct tnode TN; 6 typedef struct tnode* TT; 7 struct tnode{ 8 int data; 9 TT left,right; 10 }; 11 void creatree(TT &k) //前序遍历建立二叉树 12 { 13 int data1; 14 printf("请输入该分支的头节点："); 15 cin >> data1; 16 if (data1 ==-1) 17 k = NULL; 18 else{ 19 k = (TT)malloc(sizeof(TN)); 20 k->data = data1; 21 creatree(k->left); 22 creatree(k->right); 23 } 24 } 25 void preorder(TT root) //前序遍历 26 { 27 if (root){ 28 printf("%d ", root->data); 29 preorder(root->left); 30 preorder(root->right); 31 } 32 } 33 ////////////四种非递归遍历方法 34 35 void preorder2(TT root) //前序遍历 36 { 37 stack<TT> sk; 38 TT wk = root; 39 while (wk || !sk.empty()) 40 { 41 while (wk) //直到左子树为空的时候 42 { 43 sk.push(wk); 44 cout << wk->data << " "; 45 wk = wk->left; 46 } 47 if (!sk.empty()) 48 wk= sk.top()->right; sk.pop(); //为空时栈顶为最短父节点，遍历该父节点的右子树 49 } 50 } 51 void midorder(TT root) //中序遍历 52 { 53 TT wk = root; 54 stack<TT> sk; 55 while (wk||!sk.empty()) 56 { 57 while (wk) 58 { 59 sk.push(wk); 60 wk = wk->left; 61 } 62 if (!sk.empty()) 63 { 64 wk = sk.top(); sk.pop(); 65 cout << wk->data<<" "; 66 wk = wk->right; 67 } 68 } 69 } 70 void postorder(TT root) //后序遍历 71 { 72 stack<TT> sk; 73 TT wk = root; //工作指针 74 TT r = NULL; //标志指针 75 while (wk || !sk.empty()) 76 { 77 if (wk){ //wk非空 78 sk.push(wk); 79 wk = wk->left; 80 } 81 else 82 { 83 wk = sk.top(); 84 if (wk->right&&wk->right != r) //右子树存在且没有被访问过 85 { 86 wk = wk->right; 87 } 88 else 89 { 90 cout << wk->data << " "; 91 sk.pop(); 92 r = wk; //表示该节点已经访问 93 wk = NULL; //下一步要么结束要么wk等于栈顶元素继续访问左子树或者右子树---所以令其为空 94 } 95 } 96 } 97 } 98 //// 99 void levelorder(TT root) //层次遍历 100 { 101 queue<TT> sk; //由层次遍历的特点：左子树先访问，而且左子树的孩子也先访问 102 TT wk = root; 103 sk.push(wk); 104 while (!sk.empty()) 105 { 106 wk = sk.front(); 107 cout <<wk->data << " "; 108 if (wk->left != NULL)sk.push(wk->left); 109 if (wk->right != NULL)sk.push(wk->right); 110 sk.pop(); 111 } 112 } 113 int main() 114 { 115 TT st=NULL; 116 cout << "前序遍历建立二叉树："<<endl; 117 creatree(st); 118 cout << "前序遍历1：" << endl; 119 preorder(st); 120 cout << endl; 121 cout << "前序遍历2：" << endl; 122 preorder2(st); 123 cout << endl; 124 cout << "中序遍历：" << endl; 125 midorder(st); 126 cout << endl; 127 cout << "后序遍历：" << endl; 128 postorder(st); 129 cout << endl; 130 cout << "层次遍历：" << endl; 131 levelorder(st); 132 return 0; 133 }
