Add 18. 4Sum

Author: LuaanNguyen

medium/18_4sum/18_4sum.go

@@ -0,0 +1,40 @@
+package four_sum
+
+import "sort"
+
+func fourSum(nums []int, target int) [][]int {
+    res := make([][]int, 0)
+    sort.Ints(nums) // Sort arr in asc order 
+
+    for i := 0; i < len(nums); i++ {
+        if i > 0 && nums[i] == nums[i - 1] { // remove duplicatefor i
+            continue
+        }
+        for j := i + 1; j < len(nums); j++ {
+            if j > i + 1 && nums[j] == nums[j - 1] { // remove duplicatefor j
+                continue
+            }
+            l := j + 1
+            r := len(nums) - 1
+            for l < r {
+                if nums[i] + nums[j] + nums[l] + nums[r] == target {
+                    res = append(res, []int{nums[i], nums[j], nums[l], nums[r]})
+
+                    for l < r && nums[l] == nums[l + 1] {
+                        l ++ 
+                    } 
+                    for l < r && nums[r] == nums[r - 1] {
+                        r --
+                    }
+                    l ++ 
+                    r -- 
+                } else if nums[i] + nums[j] + nums[l] + nums[r] > target {
+                    r -- 
+                } else {
+                    l ++ 
+                }
+            }
+        }
+    }
+    return res
+}

medium/18_4sum/18_4sum_test.go

@@ -0,0 +1,38 @@
+package four_sum
+
+import (
+	"reflect"
+	"testing"
+)
+
+type Problem struct {
+	name	string 
+	nums	[]int
+	target	int
+	expectedResult 	[][]int
+}
+
+func TestFourSum(t *testing.T) {
+	tests := []Problem  {
+		{
+			name: "Test Case 1",
+			nums: []int{1,0,-1,0,-2,2},
+			target: 0,
+			expectedResult: [][]int{{-2,-1,1,2},{-2,0,0,2},{-1,0,0,1}},
+		},
+		{
+			name: "Test Case 1",
+			nums: []int{1,0,-1,0,-2,2},
+			target: 0,
+			expectedResult: [][]int{{-2,-1,1,2},{-2,0,0,2},{-1,0,0,1}},
+		},
+	}
+
+	for  _, test := range tests {
+		got := fourSum(test.nums, test.target) 
+
+		if !reflect.DeepEqual(got, test.expectedResult) {
+			t.Errorf("fourSum(%v, %d) = %v, want = %v", test.nums, test.target, got, test.expectedResult)
+		}
+	}
+}