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krahets
2024-05-31 12:45:17 +08:00
parent 6bac0db1c4
commit 124c7ce24d
27 changed files with 1003 additions and 146 deletions
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docs/chapter_backtracking/backtracking_algorithm.md
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@@ -168,7 +168,7 @@ comments: true
```rust title="preorder_traversal_i_compact.rs"
/* 前序遍历：例题一 */
fn pre_order(res: &mut Vec<Rc<RefCell<TreeNode>>>, root: Option<Rc<RefCell<TreeNode>>>) {
fn pre_order(res: &mut Vec<Rc<RefCell<TreeNode>>>, root: Option<&Rc<RefCell<TreeNode>>>) {
if root.is_none() {
return;
}
@@ -177,8 +177,8 @@ comments: true
// 记录解
res.push(node.clone());
}
pre_order(res, node.borrow().left.clone());
pre_order(res, node.borrow().right.clone());
pre_order(res, node.borrow().left.as_ref());
pre_order(res, node.borrow().right.as_ref());
}
}
```
@@ -463,7 +463,7 @@ comments: true
fn pre_order(
res: &mut Vec<Vec<Rc<RefCell<TreeNode>>>>,
path: &mut Vec<Rc<RefCell<TreeNode>>>,
root: Option<Rc<RefCell<TreeNode>>>,
root: Option<&Rc<RefCell<TreeNode>>>,
) {
if root.is_none() {
return;
@@ -475,10 +475,10 @@ comments: true
// 记录解
res.push(path.clone());
}
pre_order(res, path, node.borrow().left.clone());
pre_order(res, path, node.borrow().right.clone());
pre_order(res, path, node.borrow().left.as_ref());
pre_order(res, path, node.borrow().right.as_ref());
// 回退
path.remove(path.len() - 1);
path.pop();
}
}
```
@@ -819,7 +819,7 @@ comments: true
fn pre_order(
res: &mut Vec<Vec<Rc<RefCell<TreeNode>>>>,
path: &mut Vec<Rc<RefCell<TreeNode>>>,
root: Option<Rc<RefCell<TreeNode>>>,
root: Option<&Rc<RefCell<TreeNode>>>,
) {
// 剪枝
if root.is_none() || root.as_ref().unwrap().borrow().val == 3 {
@@ -832,10 +832,10 @@ comments: true
// 记录解
res.push(path.clone());
}
pre_order(res, path, node.borrow().left.clone());
pre_order(res, path, node.borrow().right.clone());
pre_order(res, path, node.borrow().left.as_ref());
pre_order(res, path, node.borrow().right.as_ref());
// 回退
path.remove(path.len() - 1);
path.pop();
}
}
```
@@ -1732,7 +1732,7 @@ comments: true
```rust title="preorder_traversal_iii_template.rs"
/* 判断当前状态是否为解 */
fn is_solution(state: &mut Vec<Rc<RefCell<TreeNode>>>) -> bool {
return !state.is_empty() && state.get(state.len() - 1).unwrap().borrow().val == 7;
return !state.is_empty() && state.last().unwrap().borrow().val == 7;
}
/* 记录解 */
@@ -1744,8 +1744,8 @@ comments: true
}
/* 判断在当前状态下，该选择是否合法 */
fn is_valid(_: &mut Vec<Rc<RefCell<TreeNode>>>, choice: Rc<RefCell<TreeNode>>) -> bool {
return choice.borrow().val != 3;
fn is_valid(_: &mut Vec<Rc<RefCell<TreeNode>>>, choice: Option<&Rc<RefCell<TreeNode>>>) -> bool {
return choice.is_some() && choice.unwrap().borrow().val != 3;
}
/* 更新状态 */
@@ -1755,13 +1755,13 @@ comments: true
/* 恢复状态 */
fn undo_choice(state: &mut Vec<Rc<RefCell<TreeNode>>>, _: Rc<RefCell<TreeNode>>) {
state.remove(state.len() - 1);
state.pop();
}
/* 回溯算法：例题三 */
fn backtrack(
state: &mut Vec<Rc<RefCell<TreeNode>>>,
choices: &mut Vec<Rc<RefCell<TreeNode>>>,
choices: &Vec<Option<&Rc<RefCell<TreeNode>>>>,
res: &mut Vec<Vec<Rc<RefCell<TreeNode>>>>,
) {
// 检查是否为解
@@ -1770,22 +1770,22 @@ comments: true
record_solution(state, res);
}
// 遍历所有选择
for choice in choices {
for &choice in choices.iter() {
// 剪枝：检查选择是否合法
if is_valid(state, choice.clone()) {
if is_valid(state, choice) {
// 尝试：做出选择，更新状态
make_choice(state, choice.clone());
make_choice(state, choice.unwrap().clone());
// 进行下一轮选择
backtrack(
state,
&mut vec![
choice.borrow().left.clone().unwrap(),
choice.borrow().right.clone().unwrap(),
&vec![
choice.unwrap().borrow().left.as_ref(),
choice.unwrap().borrow().right.as_ref(),
],
res,
);
// 回退：撤销选择，恢复到之前的状态
undo_choice(state, choice.clone());
undo_choice(state, choice.unwrap().clone());
}
}
}