Merge pull request #1429 from wzqwtt/backtracking02

添加(0216.组合总和III、0017.电话号码的字母组合) Scala版本
This commit is contained in:
程序员Carl
2022-07-07 09:01:28 +08:00
committed by GitHub
2 changed files with 61 additions and 0 deletions

View File

@ -557,6 +557,37 @@ func letterCombinations(_ digits: String) -> [String] {
}
```
## Scala:
```scala
object Solution {
import scala.collection.mutable
def letterCombinations(digits: String): List[String] = {
var result = mutable.ListBuffer[String]()
if(digits == "") return result.toList // 如果参数为空返回空结果集的List形式
var path = mutable.ListBuffer[Char]()
// 数字和字符的映射关系
val map = Array[String]("", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz")
def backtracking(index: Int): Unit = {
if (index == digits.size) {
result.append(path.mkString) // mkString语法将数组类型直接转换为字符串
return
}
var digit = digits(index) - '0' // 这里使用toInt会报错必须 -'0'
for (i <- 0 until map(digit).size) {
path.append(map(digit)(i))
backtracking(index + 1)
path = path.take(path.size - 1)
}
}
backtracking(0)
result.toList
}
}
```
-----------------------
<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

View File

@ -502,5 +502,35 @@ func combinationSum3(_ count: Int, _ targetSum: Int) -> [[Int]] {
}
```
## Scala
```scala
object Solution {
import scala.collection.mutable
def combinationSum3(k: Int, n: Int): List[List[Int]] = {
var result = mutable.ListBuffer[List[Int]]()
var path = mutable.ListBuffer[Int]()
def backtracking(k: Int, n: Int, sum: Int, startIndex: Int): Unit = {
if (sum > n) return // 剪枝如果sum>目标和,就返回
if (sum == n && path.size == k) {
result.append(path.toList)
return
}
// 剪枝
for (i <- startIndex to (9 - (k - path.size) + 1)) {
path.append(i)
backtracking(k, n, sum + i, i + 1)
path = path.take(path.size - 1)
}
}
backtracking(k, n, 0, 1) // 调用递归方法
result.toList // 最终返回结果集的List形式
}
}
```
-----------------------
<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>