algorithm/hello-algo
1
0
Fork 0
mirror of https://github.com/krahets/hello-algo.git synced 2025-07-14 19:41:41 +08:00
Code Issues Packages Projects Releases Wiki Activity

build

Browse Source
This commit is contained in:
krahets
2023-04-23 14:58:03 +08:00
parent 881ece517f
commit fe8027e64a
26 changed files with 344 additions and 626 deletions
Download Patch File Download Diff File Expand all files Collapse all files

54
chapter_backtracking/backtracking_algorithm.md
View File

@ -88,14 +88,11 @@ comments: true
```csharp title="preorder_traversal_i_compact.cs"
/* 前序遍历：例题一 */
void preOrder(TreeNode root)
{
if (root == null)
{
void preOrder(TreeNode root) {
if (root == null) {
return;
}
if (root.val == 7)
{
if (root.val == 7) {
// 记录解
res.Add(root);
}
@ -220,16 +217,13 @@ comments: true
```csharp title="preorder_traversal_ii_compact.cs"
/* 前序遍历：例题二 */
void preOrder(TreeNode root)
{
if (root == null)
{
void preOrder(TreeNode root) {
if (root == null) {
return;
}
// 尝试
path.Add(root);
if (root.val == 7)
{
if (root.val == 7) {
// 记录解
res.Add(new List<TreeNode>(path));
}
@ -386,17 +380,14 @@ comments: true
```csharp title="preorder_traversal_iii_compact.cs"
/* 前序遍历：例题三 */
void preOrder(TreeNode root)
{
void preOrder(TreeNode root) {
// 剪枝
if (root == null || root.val == 3)
{
if (root == null || root.val == 3) {
return;
}
// 尝试
path.Add(root);
if (root.val == 7)
{
if (root.val == 7) {
// 记录解
res.Add(new List<TreeNode>(path));
}
@ -679,51 +670,42 @@ def backtrack(state, choices, res):
```csharp title="preorder_traversal_iii_template.cs"
/* 判断当前状态是否为解 */
bool isSolution(List<TreeNode> state)
{
bool isSolution(List<TreeNode> state) {
return state.Count != 0 && state[^1].val == 7;
}
/* 记录解 */
void recordSolution(List<TreeNode> state, List<List<TreeNode>> res)
{
void recordSolution(List<TreeNode> state, List<List<TreeNode>> res) {
res.Add(new List<TreeNode>(state));
}
/* 判断在当前状态下，该选择是否合法 */
bool isValid(List<TreeNode> state, TreeNode choice)
{
bool isValid(List<TreeNode> state, TreeNode choice) {
return choice != null && choice.val != 3;
}
/* 更新状态 */
void makeChoice(List<TreeNode> state, TreeNode choice)
{
void makeChoice(List<TreeNode> state, TreeNode choice) {
state.Add(choice);
}
/* 恢复状态 */
void undoChoice(List<TreeNode> state, TreeNode choice)
{
void undoChoice(List<TreeNode> state, TreeNode choice) {
state.RemoveAt(state.Count - 1);
}
/* 回溯算法：例题三 */
void backtrack(List<TreeNode> state, List<TreeNode> choices, List<List<TreeNode>> res)
{
void backtrack(List<TreeNode> state, List<TreeNode> choices, List<List<TreeNode>> res) {
// 检查是否为解
if (isSolution(state))
{
if (isSolution(state)) {
// 记录解
recordSolution(state, res);
return;
}
// 遍历所有选择
foreach (TreeNode choice in choices)
{
foreach (TreeNode choice in choices) {
// 剪枝：检查选择是否合法
if (isValid(state, choice))
{
if (isValid(state, choice)) {
// 尝试：做出选择，更新状态
makeChoice(state, choice);
List<TreeNode> nextChoices = new List<TreeNode>() { choice.left, choice.right };