root07 引言
在计算机科学中，二叉树是一种重要的数据结构，广泛应用于各种算法和数据管理系统中。森林是一组不相交的树，二叉树转换为森林是一个常见且有用的操作。本文将详细阐述二叉树转换为森林的规则，为读者提供深入的理解和指导。
递归分割
```
if (node == NULL) {
return NULL;
node->left = convert(node->left);
node->right = convert(node->right);
if (node->left == NULL && node->right == NULL) {
return node;
} else if (node->left == NULL) {
return node->right;
} else if (node->right == NULL) {
return node->left;
} else {
return node;
```
栈
```
stack
s.push(root);
while (!s.empty()) {
TreeNode node = s.top();
s.pop();
if (node->left == NULL && node->right == NULL) {
continue;
}
if (node->right != NULL) {
s.push(node->right);
}
if (node->left != NULL) {
s.push(node->left);
}
if (node->left == NULL || node->right == NULL) {
node->left = NULL;
node->right = NULL;
}
```
记录父节点
```
TreeNode convert(TreeNode root) {
TreeNode dummy = new TreeNode(0);
TreeNode prev = dummy;
stack
s.push(root);
while (!s.empty()) {
TreeNode node = s.top();
s.pop();
if (node->left == NULL && node->right == NULL) {
prev->right = node;
prev = prev->right;
} else {
if (node->right != NULL) {
s.push(node->right);
}
if (node->left != NULL) {
s.push(node->left);
}
}
}
return dummy->right;
```
逐层转换
```
queue
q.push(root);
while (!q.empty()) {
int n = q.size();
for (int i = 0; i < n; i++) {
TreeNode node = q.front();
q.pop();
if (node->left != NULL) {
q.push(node->left);
}
if (node->right != NULL) {
q.push(node->right);
}
node->left = NULL;
node->right = NULL;
}
```
标记法
```
void convert(TreeNode root) {
if (root == NULL) {
return;
}
convert(root->left);
convert(root->right);
root->left = NULL;
if (root->right != NULL) {
root->right = root->right->right;
}
```
节点拆分法
```
TreeNode convert(TreeNode root) {
if (root == NULL) {
return NULL;
}
if (root->left == NULL && root->right == NULL) {
return root;
}
TreeNode left = convert(root->left);
TreeNode right = convert(root->right);
root->left = NULL;
root->right = NULL;
if (left != NULL) {
left->right = right;
return left;
} else {
return right;
}
```
递归合并
```
TreeNode convert(TreeNode root) {
if (root == NULL) {
return NULL;
}
if (root->left == NULL && root->right == NULL) {
return root;
}
TreeNode left = convert(root->left);
TreeNode right = convert(root->right);
if (left == NULL) {
root->right = right;
return root;
} else if (right == NULL) {
root->left = left;
return root;
} else {
root->left = left;
root->right = right;
return root;
}
```
深度优先合并
```
void convert(TreeNode root) {
if (root == NULL) {
return;
}
convert(root->left);
convert(root->right);
if (root->left != NULL && root->left->right == NULL) {
root->left->right = root->right;
root->right = NULL;
}
```
广度优先合并
```
queue
q.push(root);
while (!q.empty()) {
TreeNode node = q.front();
q.pop();
if (node->left != NULL) {
q.push(node->left);
}
if (node->right != NULL) {
q.push(node->right);
}
if (node->left != NULL && node->left->right == NULL) {
node->left->right = node->right;
node->right = NULL;
}
```
层次遍历合并
```
queue
q.push(root);
while (!q.empty()) {
int n = q.size();
for (int i = 0; i < n; i++) {
TreeNode node = q.front();
q.pop();
if (node->left != NULL) {
q.push(node->left);
}
if (node->right != NULL) {
q.push(node->right);
}
if (node->left != NULL && node->left->right == NULL) {
node->left->right = node->right;
node->right = NULL;
}
}
```
边界合并
```
void convert(TreeNode root) {
if (root == NULL) {
return;
}
convert(root->left);
convert(root->right);
if (root->left != NULL) {
TreeNode node = root->left;
while (node->right != NULL) {
node = node->right;
}
node->right = root->right;
root->right = NULL;
}
```
逆序合并
```
void convert(TreeNode root) {
if (root == NULL) {
return;
}
convert(root->right);
convert(root->left);
if (root->right != NULL) {
TreeNode node = root->right;
while (node->left != NULL) {
node = node->left;
}
node->left = root->left;
root->left = NULL;
}
```
二叉树转换为森林的规则涉及多种技术和策略，包括递归、遍历和合并。通过对每个规则的深入理解，读者可以有效地转换二叉树，满足特定问题的需求。这些规则为开发高效和灵活的算法提供了基础，广泛应用于计算机科学和相关领域。
