From 4068040965153cbcbdd970be6abf5fa31be517f0 Mon Sep 17 00:00:00 2001
From: ltinyho <ltinyho@gmail.com>
Date: Tue, 3 Aug 2021 14:43:44 +0800
Subject: [PATCH] =?UTF-8?q?0018.=E5=9B=9B=E6=95=B0=E4=B9=8B=E5=92=8C-golan?=
 =?UTF-8?q?g?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 problems/0018.四数之和.md | 48 +++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/problems/0018.四数之和.md b/problems/0018.四数之和.md
index 0caf12be..4a8fa947 100644
--- a/problems/0018.四数之和.md
+++ b/problems/0018.四数之和.md
@@ -201,6 +201,54 @@ class Solution(object):
 ```
 
 Go：
+```go
+func fourSum(nums []int, target int) [][]int {
+	if len(nums) < 4 {
+		return nil
+	}
+	sort.Ints(nums)
+	var res [][]int
+	for i := 0; i < len(nums)-3; i++ {
+		n1 := nums[i]
+		// if n1 > target { // 不能这样写,因为可能是负数
+		// 	break
+		// }
+		if i > 0 && n1 == nums[i-1] {
+			continue
+		}
+		for j := i + 1; j < len(nums)-2; j++ {
+			n2 := nums[j]
+			if j > i+1 && n2 == nums[j-1] {
+				continue
+			}
+			l := j + 1
+			r := len(nums) - 1
+			for l < r {
+				n3 := nums[l]
+				n4 := nums[r]
+				sum := n1 + n2 + n3 + n4
+				if sum < target {
+					l++
+				} else if sum > target {
+					r--
+				} else {
+					res = append(res, []int{n1, n2, n3, n4})
+					for l < r && n3 == nums[l+1] { // 去重
+						l++
+					}
+					for l < r && n4 == nums[r-1] { // 去重
+						r--
+					}
+					// 找到答案时,双指针同时靠近
+					r--
+					l++
+				}
+			}
+		}
+	}
+	return res
+}
+```
 
 javaScript: