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56b20eff36
* .net 8.0 migration * update docs * revert change * revert change and update appendix docs * remove static * Update binary_search_insertion.cs * Update binary_search_insertion.cs * Update binary_search_edge.cs * Update binary_search_insertion.cs * Update binary_search_edge.cs --------- Co-authored-by: Yudong Jin <krahets@163.com>
72 lines
2.3 KiB
C#
72 lines
2.3 KiB
C#
/**
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* File: preorder_traversal_iii_template.cs
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* Created Time: 2023-04-17
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* Author: hpstory (hpstory1024@163.com)
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*/
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namespace hello_algo.chapter_backtracking;
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public class preorder_traversal_iii_template {
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/* 判断当前状态是否为解 */
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bool IsSolution(List<TreeNode> state) {
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return state.Count != 0 && state[^1].val == 7;
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}
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/* 记录解 */
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void RecordSolution(List<TreeNode> state, List<List<TreeNode>> res) {
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res.Add(new List<TreeNode>(state));
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}
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/* 判断在当前状态下,该选择是否合法 */
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bool IsValid(List<TreeNode> state, TreeNode choice) {
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return choice != null && choice.val != 3;
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}
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/* 更新状态 */
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void MakeChoice(List<TreeNode> state, TreeNode choice) {
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state.Add(choice);
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}
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/* 恢复状态 */
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void UndoChoice(List<TreeNode> state, TreeNode choice) {
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state.RemoveAt(state.Count - 1);
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}
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/* 回溯算法:例题三 */
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void Backtrack(List<TreeNode> state, List<TreeNode> choices, List<List<TreeNode>> res) {
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// 检查是否为解
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if (IsSolution(state)) {
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// 记录解
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RecordSolution(state, res);
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}
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// 遍历所有选择
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foreach (TreeNode choice in choices) {
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// 剪枝:检查选择是否合法
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if (IsValid(state, choice)) {
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// 尝试:做出选择,更新状态
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MakeChoice(state, choice);
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// 进行下一轮选择
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Backtrack(state, [choice.left!, choice.right!], res);
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// 回退:撤销选择,恢复到之前的状态
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UndoChoice(state, choice);
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}
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}
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}
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[Test]
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public void Test() {
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TreeNode? root = TreeNode.ListToTree([1, 7, 3, 4, 5, 6, 7]);
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Console.WriteLine("\n初始化二叉树");
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PrintUtil.PrintTree(root);
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// 回溯算法
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List<List<TreeNode>> res = [];
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List<TreeNode> choices = [root!];
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Backtrack([], choices, res);
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Console.WriteLine("\n输出所有根节点到节点 7 的路径,要求路径中不包含值为 3 的节点");
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foreach (List<TreeNode> path in res) {
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PrintUtil.PrintList(path.Select(p => p.val).ToList());
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}
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}
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}
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