add: 3sum solution in go (#37)

Author: cosmicray001

README.md

@@ -18,7 +18,7 @@ LeetCode
 |0012|[Integer to Roman](https://leetcode.com/problems/integer-to-roman) || [c++](./src/0012-Integer-to-Roman/0012.cpp) |[python](./src/0012-Integer-to-Roman/0012.py)|[go](./src/0012-Integer-to-Roman/0012.go)||||Medium|
 |0013|[Roman to Integer](https://leetcode.com/problems/roman-to-integer/) || [c++](./src/0013-Roman-to-Integer/0013.cpp) |[python](./src/0013-Roman-to-Integer/0013.py)|[go](./src/0013-Roman-to-Integer/0013.go)|[js](./src/0013-Roman-to-Integer/0013.js)|[java](./src/0013-Roman-to-Integer/0013.java)||Easy|
 |0014|[Longest Common Prefix](https://leetcode.com/problems/longest-common-prefix/) || [c++](./src/0014-Longest-Common-Prefix/0014.cpp) |[python](./src/0014-Longest-Common-Prefix/0014.py)|[go](./src/0014-Longest-Common-Prefix/0014.go)||||Easy|
-|0015|[3Sum](https://leetcode.com/problems/3sum/) || [c++](./src/0015-3Sum/0015.cpp) |[python](./src/0015-3Sum/0015.py)|||||Medium|
+|0015|[3Sum](https://leetcode.com/problems/3sum/) || [c++](./src/0015-3Sum/0015.cpp) |[python](./src/0015-3Sum/0015.py)|[go](./src/0015-3Sum/0015.go)||||Medium|
 |0016|[3Sum Closest](https://leetcode.com/problems/3Sum-Closest/) || [c++](./src/0016-3Sum-Closest/0016.cpp) |[python](./src/0016-3Sum-Closest/0016.py)|||||Medium|
 |0017|[Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/) || [c++](./src/0017-Letter-Combinations-of-a-Phone-Number/0017.cpp) |[python](./src/0017-Letter-Combinations-of-a-Phone-Number/0017.py)|||||Medium|   
 |0018|[4Sum](https://leetcode.com/problems/4sum/) || [c++](./src/0018-4Sum/0018.cpp) |[python](./src/0018-4Sum/0018.py)|||||Medium|

src/0015-3Sum/0015.go

@@ -0,0 +1,38 @@
+package sum
+
+import (
+	"sort"
+)
+
+func threeSum(nums []int) [][]int {
+	ans := make([][]int, 0)
+	if len(nums) < 3 {
+		return ans
+	}
+	sort.Ints(nums)
+	for i := 0; i < len(nums)-2; i++ {
+		if i > 0 && nums[i] == nums[i-1] {
+			continue
+		}
+		lo, hi := i+1, len(nums)-1
+		for lo < hi {
+			val := nums[i] + nums[lo] + nums[hi]
+			if val > 0 {
+				hi--
+			} else if val < 0 {
+				lo++
+			} else {
+				temp := []int{nums[i], nums[lo], nums[hi]}
+				ans = append(ans, temp)
+				lo1, hi1 := lo, hi
+				for lo < hi && nums[lo] == nums[lo1] {
+					lo++
+				}
+				for lo < hi && nums[hi] == nums[hi1] {
+					hi--
+				}
+			}
+		}
+	}
+	return ans
+}