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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
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@ -557,6 +557,37 @@ func letterCombinations(_ digits: String) -> [String] {
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}
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```
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## Scala:
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```scala
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object Solution {
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import scala.collection.mutable
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def letterCombinations(digits: String): List[String] = {
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var result = mutable.ListBuffer[String]()
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if(digits == "") return result.toList // 如果参数为空,返回空结果集的List形式
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var path = mutable.ListBuffer[Char]()
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// 数字和字符的映射关系
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val map = Array[String]("", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz")
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def backtracking(index: Int): Unit = {
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if (index == digits.size) {
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result.append(path.mkString) // mkString语法:将数组类型直接转换为字符串
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return
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}
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var digit = digits(index) - '0' // 这里使用toInt会报错!必须 -'0'
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for (i <- 0 until map(digit).size) {
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path.append(map(digit)(i))
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backtracking(index + 1)
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path = path.take(path.size - 1)
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}
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}
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backtracking(0)
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result.toList
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}
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}
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```
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-----------------------
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<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>
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@ -502,5 +502,35 @@ func combinationSum3(_ count: Int, _ targetSum: Int) -> [[Int]] {
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}
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```
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## Scala
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```scala
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object Solution {
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import scala.collection.mutable
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def combinationSum3(k: Int, n: Int): List[List[Int]] = {
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var result = mutable.ListBuffer[List[Int]]()
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var path = mutable.ListBuffer[Int]()
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def backtracking(k: Int, n: Int, sum: Int, startIndex: Int): Unit = {
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if (sum > n) return // 剪枝,如果sum>目标和,就返回
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if (sum == n && path.size == k) {
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result.append(path.toList)
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return
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}
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// 剪枝
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for (i <- startIndex to (9 - (k - path.size) + 1)) {
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path.append(i)
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backtracking(k, n, sum + i, i + 1)
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path = path.take(path.size - 1)
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}
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}
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backtracking(k, n, 0, 1) // 调用递归方法
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result.toList // 最终返回结果集的List形式
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}
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}
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```
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-----------------------
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<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>
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