二叉树常见算法

  1 typedef struct node{
  2     int val;
  3     struct node *left, *right;
  4 }TreeNode;
  5 //求二叉树的节点个数。
  6 int GetNodeNum(TreeNode *pRoot){
  7     if(pRoot == NULL)
  8         return 0;
  9     return GetNodeNum(pRoot->left) + GetNodeNum(pRoot->right) +;
 10 }
 11 //求二叉树的深度
 12 int GetDepth(TreeNode* root){
 13     if(root == NULL)
 14         return 0;
 15     int depth_left = GetDepth(root->left);
 16     int depth_right = GetDepth(root->right);
 17     return max(depth_right, depth_left) + 1;
 18 }
 19 //三种遍历方式
 20 void PreOrderTraverse(TreeNode *root){
 21     if(root == NULL)
 22         return;
 23     visit(root->val);
 24     PreOrderTraverse(root->left);
 25     PreOrderTraverse(root->right);
 26 }
 27 void InOrderTraverse(TreeNode *root){
 28     if(root == NULL)
 29         return;
 30     InOrderTraverse(root->left);
 31     visit(root->val);
 32     InOrderTraverse(root->right);
 33 }
 34 void PostOrderTraverse(TreeNode *root){
 35     if(root == NULL)
 36         return;
 37     PostOrderTraverse(root->left);
 38     PostOrderTraverse(root->right);
 39     visit(root->val);
 40 }
 41 //层序遍历二叉树
 42 void LevelTraverse(TreeNode *root){
 43     if(root == NULL)
 44         return;
 45     queue<TreeNode*> q;
 46     q.push(root);
 47     while(!q.empty()){
 48         TreeNode *node = q.front();
 49         q.pop();
 50         visit(root->val);
 51         if(node->left != NULL)
 52             q.push(node->left);
 53         if(node->right != NULL)
 54             q.push(node->right);
 55     }
 56     return;
 57 }
 58 //求二叉树第k层的节点数
 59 int GetNodeNumKthLevel(TreeNode *root, int k){
 60     if(root == NULL || k < 1)
 61         return 0;
 62     if(k == 1)
 63         return 1;
 64     int numLeft = GetNodeNumKthLevel(root->left, k - 1);
 65     int numRight = GetNodeNumKthLevel(root->right, k - 1);
 66     return (numLeft + numRight);
 67 }
 68 //求二叉树叶子节点个数
 69 int GetLeafNodeNum(TreeNode *root){
 70     if(root == NULL)
 71         return 0;
 72     if(root->left == NULL && root->right == NULL)
 73         return 1;
 74     int numLeft = GetLeafNodeNum(root->left);
 75     int numRight = GetLeafNodeNum(root->right);
 76     return (numLeft + numRight);
 77 
 78 }
 79 //判断两颗二叉树是否结构相同
 80 bool isSame(TreeNode *tree1, TreeNode *tree2){
 81     if(tree1 == NULL && tree2 == NULL)
 82         return true;
 83     if(tree1 == NULL && tree2 != NULL || tree1 != NULL && tree2 == NULL ||
 84         tree1->val != tree2->val)
 85         return false;
 86     return isSame(tree1->left, tree2->left) && isSame(tree1->right, tree2->right);
 87 }
 88 //判断二叉树是否是平衡二叉树
 89 bool IsAVL(TreeNode *root, int &height){
 90     if(root == NULL){
 91         height = 0;
 92         return true;
 93     }
 94     int heightLeft;
 95     bool resultLeft = IsAVL(root->left, heightLeft);
 96     int heightRight;
 97     bool resultRight;
 98     bool resultRight = IsAVL(root->right, heightRight);
 99     height = max(heightLeft, heightRight) + 1;
100     if(resultLeft && resultRight && (abs(heightLeft - heightRight) <= 1)){
101         return true;
102     } else {
103         return false;
104     }
105 }
106 //求二叉树的镜像
107 void mirror(TreeNode *root){
108     if(root == NULL)
109         return;
110     if(root->left == NULL && root->right == NULL)
111         return;
112     TreeNode *temp;
113     temp = root->left;
114     root->left = root->right;
115     root->right = temp;
116     mirror(root->left);
117     mirror(root->right);
118 }
119 //求二叉树中两个节点的最低公共祖先节点
120 
121 //求二叉树中节点的最大距离
122 //由前序遍历和中序遍历重建二叉树
123 //判断二叉树是不是完全二叉树
124 //将二叉查找树变为有序的双向链表