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954c45864b
* docs: add Japanese documents (`ja/docs`) * docs: add Japanese documents (`ja/codes`) * docs: add Japanese documents * Remove pythontutor blocks in ja/ * Add an empty at the end of each markdown file. * Add the missing figures (use the English version temporarily). * Add index.md for Japanese version. * Add index.html for Japanese version. * Add missing index.assets * Fix backtracking_algorithm.md for Japanese version. * Add avatar_eltociear.jpg. Fix image links on the Japanese landing page. * Add the Japanese banner. --------- Co-authored-by: krahets <krahets@163.com>
51 lines
1.6 KiB
C++
51 lines
1.6 KiB
C++
/**
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* File: build_tree.cpp
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* Created Time: 2023-07-17
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* Author: krahets (krahets@163.com)
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*/
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#include "../utils/common.hpp"
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/* 二分木の構築：分割統治 */
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TreeNode *dfs(vector<int> &preorder, unordered_map<int, int> &inorderMap, int i, int l, int r) {
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// 部分木の区間が空の場合に終了
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if (r - l < 0)
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return NULL;
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// ルートノードを初期化
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TreeNode *root = new TreeNode(preorder[i]);
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// m を問い合わせて左右の部分木を分割
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int m = inorderMap[preorder[i]];
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// 部分問題：左の部分木を構築
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root->left = dfs(preorder, inorderMap, i + 1, l, m - 1);
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// 部分問題：右の部分木を構築
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root->right = dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r);
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// ルートノードを返す
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return root;
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}
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/* 二分木の構築 */
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TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
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// ハッシュテーブルを初期化し、中間順序の要素からインデックスへのマッピングを格納
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unordered_map<int, int> inorderMap;
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for (int i = 0; i < inorder.size(); i++) {
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inorderMap[inorder[i]] = i;
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}
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TreeNode *root = dfs(preorder, inorderMap, 0, 0, inorder.size() - 1);
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return root;
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}
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/* ドライバーコード */
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int main() {
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vector<int> preorder = {3, 9, 2, 1, 7};
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vector<int> inorder = {9, 3, 1, 2, 7};
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cout << "前順走査 = ";
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printVector(preorder);
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cout << "中間順序走査 = ";
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printVector(inorder);
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TreeNode *root = buildTree(preorder, inorder);
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cout << "構築された二分木:\n";
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printTree(root);
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return 0;
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} |