From 68eed4af5b1f43e7ac65093dd00c7497f88885cc Mon Sep 17 00:00:00 2001
From: ZongqinWang <1722249371@qq.com>
Date: Sat, 14 May 2022 15:26:29 +0800
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200018.=E5=9B=9B=E6=95=B0?=
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---
 problems/0018.四数之和.md | 45 ++++++++++++++++++++++++++++++++++-
 1 file changed, 44 insertions(+), 1 deletion(-)

diff --git a/problems/0018.四数之和.md b/problems/0018.四数之和.md
index ee70cb69..6cbd40c2 100644
--- a/problems/0018.四数之和.md
+++ b/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>