Merge pull request #1328 from wzqwtt/patch09

添加（0015.三数之和、0018.四数之和）Scala版本

problems/0015.三数之和.md

@@ -616,6 +616,49 @@ public class Solution
     }
 }
 ```
+Scala:
+```scala
+object Solution {
+  // 导包
+  import scala.collection.mutable.ListBuffer
+  import scala.util.control.Breaks.{break, breakable}
 
+  def threeSum(nums: Array[Int]): List[List[Int]] = {
+    // 定义结果集，最后需要转换为List
+    val res = ListBuffer[List[Int]]()
+    val nums_tmp = nums.sorted // 对nums进行排序
+    for (i <- nums_tmp.indices) {
+      // 如果要排的第一个数字大于0，直接返回结果
+      if (nums_tmp(i) > 0) {
+        return res.toList
+      }
+      // 如果i大于0并且和前一个数字重复，则跳过本次循环，相当于continue
+      breakable {
+        if (i > 0 && nums_tmp(i) == nums_tmp(i - 1)) {
+          break
+        } else {
+          var left = i + 1
+          var right = nums_tmp.length - 1
+          while (left < right) {
+            var sum = nums_tmp(i) + nums_tmp(left) + nums_tmp(right) // 求三数之和
+            if (sum < 0) left += 1
+            else if (sum > 0) right -= 1
+            else {
+              res += List(nums_tmp(i), nums_tmp(left), nums_tmp(right)) // 如果等于0 添加进结果集
+              // 为了避免重复，对left和right进行移动
+              while (left < right && nums_tmp(left) == nums_tmp(left + 1)) left += 1
+              while (left < right && nums_tmp(right) == nums_tmp(right - 1)) right -= 1
+              left += 1
+              right -= 1
+            }
+          }
+        }
+      }
+    }
+    // 最终返回需要转换为List，return关键字可以省略
+    res.toList
+  }
+}
+```
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/0018.四数之和.md

@@ -522,6 +522,49 @@ public class Solution
     }
 }
 ```
-
+Scala:
+```scala
+object Solution {
+  // 导包
+  import scala.collection.mutable.ListBuffer
+  import scala.util.control.Breaks.{break, breakable}
+  def fourSum(nums: Array[Int], target: Int): List[List[Int]] = {
+    val res = ListBuffer[List[Int]]()
+    val nums_tmp = nums.sorted // 先排序
+    for (i <- nums_tmp.indices) {
+      breakable {
+        if (i > 0 && nums_tmp(i) == nums_tmp(i - 1)) {
+          break // 如果该值和上次的值相同，跳过本次循环，相当于continue
+        } else {
+          for (j <- i + 1 until nums_tmp.length) {
+            breakable {
+              if (j > i + 1 && nums_tmp(j) == nums_tmp(j - 1)) {
+                break // 同上
+              } else {
+                // 双指针
+                var (left, right) = (j + 1, nums_tmp.length - 1)
+                while (left < right) {
+                  var sum = nums_tmp(i) + nums_tmp(j) + nums_tmp(left) + nums_tmp(right)
+                  if (sum == target) {
+                    // 满足要求，直接加入到集合里面去
+                    res += List(nums_tmp(i), nums_tmp(j), nums_tmp(left), nums_tmp(right))
+                    while (left < right && nums_tmp(left) == nums_tmp(left + 1)) left += 1
+                    while (left < right && nums_tmp(right) == nums_tmp(right - 1)) right -= 1
+                    left += 1
+                    right -= 1
+                  } else if (sum < target) left += 1
+                  else right -= 1
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+    // 最终返回的res要转换为List，return关键字可以省略
+    res.toList
+  }
+}
+```
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>