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Simplify kotlin code and improve code readability (#1198)

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* Add kotlin code block for chapter_hashing

* Add kotlin code block for chapter_heap.

* Add kotlin code block for chapter_stack_and_queue and chapter_tree

* fix indentation

* Update binary_tree.md

* style(kotlin): simplify code and improve readability.

* simplify kt code for chapter_computational_complexity.

* style(kotlin): replace ArrayList with MutableList.

* Update subset_sum_i.kt

Use kotlin api instead of java.

* Update subset_sum_ii.kt

use kotlin api instead of java

* style(kotlin): replace ArrayList with mutablelist.

---------

Co-authored-by: Yudong Jin <krahets@163.com>
This commit is contained in:
curtishd
2024-04-07 01:31:58 +08:00
committed by GitHub
parent 931d8f5089
commit 2655a2f66a
17 changed files with 101 additions and 101 deletions
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codes/kotlin/chapter_backtracking/n_queens.kt
+9 -9
View File
@@ -10,17 +10,17 @@ package chapter_backtracking.n_queens
fun backtrack(
row: Int,
n: Int,
state: List<MutableList<String>>,
res: MutableList<List<List<String>>?>,
state: MutableList<MutableList<String>>,
res: MutableList<MutableList<MutableList<String>>?>,
cols: BooleanArray,
diags1: BooleanArray,
diags2: BooleanArray
) {
// 当放置完所有行时，记录解
if (row == n) {
val copyState: MutableList<List<String>> = ArrayList()
val copyState = mutableListOf<MutableList<String>>()
for (sRow in state) {
copyState.add(ArrayList(sRow))
copyState.add(sRow.toMutableList())
}
res.add(copyState)
return
@@ -49,11 +49,11 @@ fun backtrack(
}
/* 求解 n 皇后 */
fun nQueens(n: Int): List<List<List<String>>?> {
fun nQueens(n: Int): MutableList<MutableList<MutableList<String>>?> {
// 初始化 n*n 大小的棋盘，其中 'Q' 代表皇后，'#' 代表空位
val state: MutableList<MutableList<String>> = ArrayList()
val state = mutableListOf<MutableList<String>>()
for (i in 0..<n) {
val row: MutableList<String> = ArrayList()
val row = mutableListOf<String>()
for (j in 0..<n) {
row.add("#")
}
@@ -62,7 +62,7 @@ fun nQueens(n: Int): List<List<List<String>>?> {
val cols = BooleanArray(n) // 记录列是否有皇后
val diags1 = BooleanArray(2 * n - 1) // 记录主对角线上是否有皇后
val diags2 = BooleanArray(2 * n - 1) // 记录次对角线上是否有皇后
val res: MutableList<List<List<String>>?> = ArrayList()
val res = mutableListOf<MutableList<MutableList<String>>?>()
backtrack(0, n, state, res, cols, diags1, diags2)
@@ -72,7 +72,7 @@ fun nQueens(n: Int): List<List<List<String>>?> {
/* Driver Code */
fun main() {
val n = 4
val res: List<List<List<String?>?>?> = nQueens(n)
val res = nQueens(n)
println("输入棋盘长宽为 $n")
println("皇后放置方案共有 ${res.size} 种")
codes/kotlin/chapter_backtracking/permutations_i.kt
+5 -5
View File
@@ -11,11 +11,11 @@ fun backtrack(
state: MutableList<Int>,
choices: IntArray,
selected: BooleanArray,
res: MutableList<List<Int>?>
res: MutableList<MutableList<Int>?>
) {
// 当状态长度等于元素数量时，记录解
if (state.size == choices.size) {
res.add(ArrayList(state))
res.add(state.toMutableList())
return
}
// 遍历所有选择
@@ -36,9 +36,9 @@ fun backtrack(
}
/* 全排列 I */
fun permutationsI(nums: IntArray): List<List<Int>?> {
val res: MutableList<List<Int>?> = ArrayList()
backtrack(ArrayList(), nums, BooleanArray(nums.size), res)
fun permutationsI(nums: IntArray): MutableList<MutableList<Int>?> {
val res = mutableListOf<MutableList<Int>?>()
backtrack(mutableListOf(), nums, BooleanArray(nums.size), res)
return res
}
codes/kotlin/chapter_backtracking/permutations_ii.kt
+4 -5
View File
@@ -15,11 +15,11 @@ fun backtrack(
) {
// 当状态长度等于元素数量时，记录解
if (state.size == choices.size) {
res.add(ArrayList(state))
res.add(state.toMutableList())
return
}
// 遍历所有选择
val duplicated: MutableSet<Int> = HashSet()
val duplicated = HashSet<Int>()
for (i in choices.indices) {
val choice = choices[i]
// 剪枝：不允许重复选择元素 且 不允许重复选择相等元素
@@ -39,15 +39,14 @@ fun backtrack(
/* 全排列 II */
fun permutationsII(nums: IntArray): MutableList<MutableList<Int>?> {
val res: MutableList<MutableList<Int>?> = ArrayList()
backtrack(ArrayList(), nums, BooleanArray(nums.size), res)
val res = mutableListOf<MutableList<Int>?>()
backtrack(mutableListOf(), nums, BooleanArray(nums.size), res)
return res
}
/* Driver Code */
fun main() {
val nums = intArrayOf(1, 2, 2)
val res = permutationsII(nums)
println("输入数组 nums = ${nums.contentToString()}")
codes/kotlin/chapter_backtracking/preorder_traversal_i_compact.kt
+3 -3
View File
@@ -31,12 +31,12 @@ fun main() {
printTree(root)
// 前序遍历
res = ArrayList()
res = mutableListOf()
preOrder(root)
println("\n输出所有值为 7 的节点")
val vals: MutableList<Int> = ArrayList()
for (node in res as ArrayList<TreeNode>) {
val vals = mutableListOf<Int>()
for (node in res!!) {
vals.add(node.value)
}
println(vals)
codes/kotlin/chapter_backtracking/preorder_traversal_ii_compact.kt
+6 -6
View File
@@ -10,7 +10,7 @@ import utils.TreeNode
import utils.printTree
var path: MutableList<TreeNode>? = null
var res: MutableList<List<TreeNode>>? = null
var res: MutableList<MutableList<TreeNode>>? = null
/* 前序遍历：例题二 */
fun preOrder(root: TreeNode?) {
@@ -21,7 +21,7 @@ fun preOrder(root: TreeNode?) {
path!!.add(root)
if (root.value == 7) {
// 记录解
res!!.add(ArrayList(path!!))
res!!.add(path!!.toMutableList())
}
preOrder(root.left)
preOrder(root.right)
@@ -36,13 +36,13 @@ fun main() {
printTree(root)
// 前序遍历
path = java.util.ArrayList<TreeNode>()
res = java.util.ArrayList<List<TreeNode>>()
path = mutableListOf()
res = mutableListOf()
preOrder(root)
println("\n输出所有根节点到节点 7 的路径")
for (path in res as ArrayList<List<TreeNode>>) {
val values: MutableList<Int> = ArrayList()
for (path in res!!) {
val values = mutableListOf<Int>()
for (node in path) {
values.add(node.value)
}
codes/kotlin/chapter_backtracking/preorder_traversal_iii_compact.kt
+6 -6
View File
@@ -10,7 +10,7 @@ import utils.TreeNode
import utils.printTree
var path: MutableList<TreeNode>? = null
var res: MutableList<List<TreeNode>>? = null
var res: MutableList<MutableList<TreeNode>>? = null
/* 前序遍历：例题三 */
fun preOrder(root: TreeNode?) {
@@ -22,7 +22,7 @@ fun preOrder(root: TreeNode?) {
path!!.add(root)
if (root.value == 7) {
// 记录解
res!!.add(ArrayList(path!!))
res!!.add(path!!.toMutableList())
}
preOrder(root.left)
preOrder(root.right)
@@ -37,13 +37,13 @@ fun main() {
printTree(root)
// 前序遍历
path = ArrayList()
res = ArrayList()
path = mutableListOf()
res = mutableListOf()
preOrder(root)
println("\n输出所有根节点到节点 7 的路径，路径中不包含值为 3 的节点")
for (path in res as ArrayList<List<TreeNode>>) {
val values: MutableList<Int> = ArrayList()
for (path in res!!) {
val values = mutableListOf<Int>()
for (node in path) {
values.add(node.value)
}
codes/kotlin/chapter_backtracking/preorder_traversal_iii_template.kt
+10 -11
View File
@@ -8,20 +8,19 @@ package chapter_backtracking.preorder_traversal_iii_template
import utils.TreeNode
import utils.printTree
import java.util.*
/* 判断当前状态是否为解 */
fun isSolution(state: List<TreeNode?>): Boolean {
fun isSolution(state: MutableList<TreeNode?>): Boolean {
return state.isNotEmpty() && state[state.size - 1]?.value == 7
}
/* 记录解 */
fun recordSolution(state: MutableList<TreeNode?>?, res: MutableList<List<TreeNode?>?>) {
res.add(state?.let { ArrayList(it) })
fun recordSolution(state: MutableList<TreeNode?>?, res: MutableList<MutableList<TreeNode?>?>) {
res.add(state!!.toMutableList())
}
/* 判断在当前状态下，该选择是否合法 */
fun isValid(state: List<TreeNode?>?, choice: TreeNode?): Boolean {
fun isValid(state: MutableList<TreeNode?>?, choice: TreeNode?): Boolean {
return choice != null && choice.value != 3
}
@@ -38,8 +37,8 @@ fun undoChoice(state: MutableList<TreeNode?>, choice: TreeNode?) {
/* 回溯算法：例题三 */
fun backtrack(
state: MutableList<TreeNode?>,
choices: List<TreeNode?>,
res: MutableList<List<TreeNode?>?>
choices: MutableList<TreeNode?>,
res: MutableList<MutableList<TreeNode?>?>
) {
// 检查是否为解
if (isSolution(state)) {
@@ -53,7 +52,7 @@ fun backtrack(
// 尝试：做出选择，更新状态
makeChoice(state, choice)
// 进行下一轮选择
backtrack(state, listOf(choice!!.left, choice.right), res)
backtrack(state, mutableListOf(choice!!.left, choice.right), res)
// 回退：撤销选择，恢复到之前的状态
undoChoice(state, choice)
}
@@ -67,12 +66,12 @@ fun main() {
printTree(root)
// 回溯算法
val res: MutableList<List<TreeNode?>?> = ArrayList()
backtrack(ArrayList(), mutableListOf(root), res)
val res = mutableListOf<MutableList<TreeNode?>?>()
backtrack(mutableListOf(), mutableListOf(root), res)
println("\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")
for (path in res) {
val vals = ArrayList<Int>()
val vals = mutableListOf<Int>()
for (node in path!!) {
if (node != null) {
vals.add(node.value)
codes/kotlin/chapter_backtracking/subset_sum_i.kt
+7 -9
View File
@@ -6,19 +6,17 @@
package chapter_backtracking.subset_sum_i
import java.util.*
/* 回溯算法：子集和 I */
fun backtrack(
state: MutableList<Int>,
target: Int,
choices: IntArray,
start: Int,
res: MutableList<List<Int>?>
res: MutableList<MutableList<Int>?>
) {
// 子集和等于 target 时，记录解
if (target == 0) {
res.add(ArrayList(state))
res.add(state.toMutableList())
return
}
// 遍历所有选择
@@ -39,11 +37,11 @@ fun backtrack(
}
/* 求解子集和 I */
fun subsetSumI(nums: IntArray, target: Int): List<List<Int>?> {
val state: MutableList<Int> = ArrayList() // 状态（子集）
Arrays.sort(nums) // 对 nums 进行排序
fun subsetSumI(nums: IntArray, target: Int): MutableList<MutableList<Int>?> {
val state = mutableListOf<Int>() // 状态（子集）
nums.sort() // 对 nums 进行排序
val start = 0 // 遍历起始点
val res: MutableList<List<Int>?> = ArrayList() // 结果列表（子集列表）
val res = mutableListOf<MutableList<Int>?>() // 结果列表（子集列表）
backtrack(state, target, nums, start, res)
return res
}
@@ -57,4 +55,4 @@ fun main() {
println("输入数组 nums = ${nums.contentToString()}, target = $target")
println("所有和等于 $target 的子集 res = $res")
}
}
codes/kotlin/chapter_backtracking/subset_sum_i_naive.kt
+6 -7
View File
@@ -12,11 +12,11 @@ fun backtrack(
target: Int,
total: Int,
choices: IntArray,
res: MutableList<List<Int>?>
res: MutableList<MutableList<Int>?>
) {
// 子集和等于 target 时，记录解
if (total == target) {
res.add(ArrayList(state))
res.add(state.toMutableList())
return
}
// 遍历所有选择
@@ -35,10 +35,10 @@ fun backtrack(
}
/* 求解子集和 I（包含重复子集） */
fun subsetSumINaive(nums: IntArray, target: Int): List<List<Int>?> {
val state: MutableList<Int> = ArrayList() // 状态（子集）
fun subsetSumINaive(nums: IntArray, target: Int): MutableList<MutableList<Int>?> {
val state = mutableListOf<Int>() // 状态（子集）
val total = 0 // 子集和
val res: MutableList<List<Int>?> = ArrayList() // 结果列表（子集列表）
val res = mutableListOf<MutableList<Int>?>() // 结果列表（子集列表）
backtrack(state, target, total, nums, res)
return res
}
@@ -47,8 +47,7 @@ fun subsetSumINaive(nums: IntArray, target: Int): List<List<Int>?> {
fun main() {
val nums = intArrayOf(3, 4, 5)
val target = 9
val res: List<List<Int>?> = subsetSumINaive(nums, target)
val res = subsetSumINaive(nums, target)
println("输入数组 nums = ${nums.contentToString()}, target = $target")
println("所有和等于 $target 的子集 res = $res")
codes/kotlin/chapter_backtracking/subset_sum_ii.kt
+7 -10
View File
@@ -6,19 +6,17 @@
package chapter_backtracking.subset_sum_ii
import java.util.*
/* 回溯算法：子集和 II */
fun backtrack(
state: MutableList<Int>,
target: Int,
choices: IntArray,
start: Int,
res: MutableList<List<Int>?>
res: MutableList<MutableList<Int>?>
) {
// 子集和等于 target 时，记录解
if (target == 0) {
res.add(ArrayList(state))
res.add(state.toMutableList())
return
}
// 遍历所有选择
@@ -44,11 +42,11 @@ fun backtrack(
}
/* 求解子集和 II */
fun subsetSumII(nums: IntArray, target: Int): List<List<Int>?> {
val state: MutableList<Int> = ArrayList() // 状态（子集）
Arrays.sort(nums) // 对 nums 进行排序
fun subsetSumII(nums: IntArray, target: Int): MutableList<MutableList<Int>?> {
val state = mutableListOf<Int>() // 状态（子集）
nums.sort() // 对 nums 进行排序
val start = 0 // 遍历起始点
val res: MutableList<List<Int>?> = ArrayList() // 结果列表（子集列表）
val res = mutableListOf<MutableList<Int>?>() // 结果列表（子集列表）
backtrack(state, target, nums, start, res)
return res
}
@@ -57,9 +55,8 @@ fun subsetSumII(nums: IntArray, target: Int): List<List<Int>?> {
fun main() {
val nums = intArrayOf(4, 4, 5)
val target = 9
val res = subsetSumII(nums, target)
println("输入数组 nums = ${nums.contentToString()}, target = $target")
println("所有和等于 $target 的子集 res = $res")
}
}