From 7cdfa03e68d8bb2d1183eae04917996a1d792f73 Mon Sep 17 00:00:00 2001 From: curtishd <131777542+curtishd@users.noreply.github.com> Date: Wed, 28 Feb 2024 01:25:38 +0800 Subject: [PATCH] Add kotlin code for the chapter of divide and conquer (#1098) * feat(kotlin):new kotlin support files * fix(kotlin): reviewed the formatting, comments and so on. * fix(kotlin): fix the indentation and format * feat(kotlin): Add kotlin code for the backtraking chapter. * fix(kotlin): fix incorrect output of preorder_traversal_iii_template.kt file * fix(kotlin): simplify kotlin codes * fix(kotlin): modify n_queens.kt for consistency. * feat(kotlin): add kotlin code for computational complexity. * fix(kotlin): remove iteration folder. * fix(kotlin): remove n_queens.kt file out of folder. * fix(kotlin): remove some folders. * style(kotlin): modified two chapters. * feat(kotlin): add kotlin code for divide and conquer. * Update build_tree.kt * Update hanota.kt * Delete codes/kotlin/chapter_backtracking directory * Delete codes/kotlin/chapter_computational_complexity directory * Delete codes/kotlin/chapter_divide_and_conquer directory * feat(kotlin): add kotlin code for divide and conquer. * Update hanota.kt --- .../binary_search_recur.kt | 49 ++++++++++++++++ .../chapter_divide_and_conquer/build_tree.kt | 49 ++++++++++++++++ .../chapter_divide_and_conquer/hanota.kt | 56 +++++++++++++++++++ 3 files changed, 154 insertions(+) create mode 100644 codes/kotlin/chapter_divide_and_conquer/binary_search_recur.kt create mode 100644 codes/kotlin/chapter_divide_and_conquer/build_tree.kt create mode 100644 codes/kotlin/chapter_divide_and_conquer/hanota.kt diff --git a/codes/kotlin/chapter_divide_and_conquer/binary_search_recur.kt b/codes/kotlin/chapter_divide_and_conquer/binary_search_recur.kt new file mode 100644 index 000000000..433d327d8 --- /dev/null +++ b/codes/kotlin/chapter_divide_and_conquer/binary_search_recur.kt @@ -0,0 +1,49 @@ +/** + * File: binary_search_recur.kt + * Created Time: 2024-01-25 + * Author: curtishd (1023632660@qq.com) + */ + +package chapter_divide_and_conquer.binary_search_recur + +/* 二分查找：问题 f(i, j) */ +fun dfs( + nums: IntArray, + target: Int, + i: Int, + j: Int +): Int { + // 若区间为空，代表无目标元素，则返回 -1 + if (i > j) { + return -1 + } + // 计算中点索引 m + val m = (i + j) / 2 + return if (nums[m] < target) { + // 递归子问题 f(m+1, j) + dfs(nums, target, m + 1, j) + } else if (nums[m] > target) { + // 递归子问题 f(i, m-1) + dfs(nums, target, i, m - 1) + } else { + // 找到目标元素，返回其索引 + m + } +} + +/* 二分查找 */ +fun binarySearch(nums: IntArray, target: Int): Int { + val n = nums.size + // 求解问题 f(0, n-1) + return dfs(nums, target, 0, n - 1) +} + +/* Driver Code */ +fun main() { + val target = 6 + val nums = intArrayOf(1, 3, 6, 8, 12, 15, 23, 26, 31, 35) + + // 二分查找（双闭区间） + val index = binarySearch(nums, target) + println("目标元素 6 的索引 = $index") +} \ No newline at end of file diff --git a/codes/kotlin/chapter_divide_and_conquer/build_tree.kt b/codes/kotlin/chapter_divide_and_conquer/build_tree.kt new file mode 100644 index 000000000..a0a31f9ad --- /dev/null +++ b/codes/kotlin/chapter_divide_and_conquer/build_tree.kt @@ -0,0 +1,49 @@ +/** + * File: build_tree.kt + * Created Time: 2024-01-25 + * Author: curtishd (1023632660@qq.com) + */ + +package chapter_divide_and_conquer.build_tree + +import utils.TreeNode +import utils.printTree + +/* 构建二叉树：分治 */ +fun dfs(preorder: IntArray, inorderMap: Map, i: Int, l: Int, r: Int): TreeNode? { + // 子树区间为空时终止 + if (r - l < 0) return null + // 初始化根节点 + val root = TreeNode(preorder[i]) + // 查询 m ，从而划分左右子树 + val m = inorderMap[preorder[i]]!! + // 子问题：构建左子树 + root.left = dfs(preorder, inorderMap, i + 1, l, m - 1) + // 子问题：构建右子树 + root.right = dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r) + // 返回根节点 + return root +} + +/* 构建二叉树 */ +fun buildTree(preorder: IntArray, inorder: IntArray): TreeNode? { + // 初始化哈希表，存储 inorder 元素到索引的映射 + val inorderMap: MutableMap = HashMap() + for (i in inorder.indices) { + inorderMap[inorder[i]] = i + } + val root = dfs(preorder, inorderMap, 0, 0, inorder.size - 1) + return root +} + +/* Driver Code */ +fun main() { + val preorder = intArrayOf(3, 9, 2, 1, 7) + val inorder = intArrayOf(9, 3, 1, 2, 7) + println("前序遍历 = " + preorder.contentToString()) + println("中序遍历 = " + inorder.contentToString()) + + val root = buildTree(preorder, inorder) + println("构建的二叉树为：") + printTree(root) +} \ No newline at end of file diff --git a/codes/kotlin/chapter_divide_and_conquer/hanota.kt b/codes/kotlin/chapter_divide_and_conquer/hanota.kt new file mode 100644 index 000000000..59c67f90e --- /dev/null +++ b/codes/kotlin/chapter_divide_and_conquer/hanota.kt @@ -0,0 +1,56 @@ +/** + * File: hanota.kt + * Created Time: 2024-1-25 + * Author: curtishd (1023632660@qq.com) + */ + +package chapter_divide_and_conquer.hanota + +/* 移动一个圆盘 */ +fun move(src: MutableList, tar: MutableList) { + // 从 src 顶部拿出一个圆盘 + val pan: Int = src.removeAt(src.size - 1) + // 将圆盘放入 tar 顶部 + tar.add(pan) +} + +/* 求解汉诺塔问题 f(i) */ +fun dfs(i: Int, src: MutableList, buf: MutableList, tar: MutableList) { + // 若 src 只剩下一个圆盘，则直接将其移到 tar + if (i == 1) { + move(src, tar) + return + } + // 子问题 f(i-1) ：将 src 顶部 i-1 个圆盘借助 tar 移到 buf + dfs(i - 1, src, tar, buf) + // 子问题 f(1) ：将 src 剩余一个圆盘移到 tar + move(src, tar) + // 子问题 f(i-1) ：将 buf 顶部 i-1 个圆盘借助 src 移到 tar + dfs(i - 1, buf, src, tar) +} + +/* 求解汉诺塔问题 */ +fun solveHanota(A: MutableList, B: MutableList, C: MutableList) { + val n = A.size + // 将 A 顶部 n 个圆盘借助 B 移到 C + dfs(n, A, B, C) +} + +/* Driver Code */ +fun main() { + // 列表尾部是柱子顶部 + val A: MutableList = ArrayList(mutableListOf(5, 4, 3, 2, 1)) + val B: MutableList = ArrayList() + val C: MutableList = ArrayList() + println("初始状态下：") + println("A = $A") + println("B = $B") + println("C = $C") + + solveHanota(A, B, C) + + println("圆盘移动完成后：") + println("A = $A") + println("B = $B") + println("C = $C") +}