Add: 4Sum

Author: openset

Diff for: problems/4sum/4sum.go

@@ -1 +1,37 @@
 package p_4sum
+
+import "sort"
+
+func fourSum(nums []int, target int) [][]int {
+	sort.Ints(nums)
+	ans, end := make([][]int, 0), len(nums)-1
+	for i := 0; i < end-2; i++ {
+		if i > 0 && nums[i] == nums[i-1] {
+			continue
+		}
+		for j := i + 1; j < end-1; j++ {
+			if j > i+1 && nums[j] == nums[j-1] {
+				continue
+			}
+			l, r := j+1, end
+			for l < r {
+				sum := nums[i] + nums[j] + nums[l] + nums[r]
+				if sum < target {
+					l++
+				} else if sum > target {
+					r--
+				} else {
+					ans = append(ans, []int{nums[i], nums[j], nums[l], nums[r]})
+					l, r = l+1, r-1
+					for l < r && nums[l] == nums[l-1] {
+						l++
+					}
+					for l < r && nums[r] == nums[r+1] {
+						r--
+					}
+				}
+			}
+		}
+	}
+	return ans
+}

Diff for: problems/4sum/4sum_test.go

@@ -1 +1,81 @@
 package p_4sum
+
+import (
+	"reflect"
+	"testing"
+)
+
+type caseType struct {
+	input    []int
+	target   int
+	expected [][]int
+}
+
+func TestFourSum(t *testing.T) {
+	tests := [...]caseType{
+		{
+			input:  []int{1, 0, -1, 0, -2, 2},
+			target: 0,
+			expected: [][]int{
+				{-2, -1, 1, 2},
+				{-2, 0, 0, 2},
+				{-1, 0, 0, 1},
+			},
+		},
+		{
+			input:  []int{-1, 0, 1, 2, -1, -4},
+			target: 0,
+			expected: [][]int{
+				{-1, -1, 0, 2},
+			},
+		},
+		{
+			input:  []int{0, 0, 0, 0},
+			target: 0,
+			expected: [][]int{
+				{0, 0, 0, 0},
+			},
+		},
+		{
+			input:  []int{-2, 0, 0, 2, 2, 2},
+			target: 0,
+			expected: [][]int{
+				{-2, 0, 0, 2},
+			},
+		},
+		{
+			input:  []int{-2, 0, 0, 2, 2, 2, 2},
+			target: 0,
+			expected: [][]int{
+				{-2, 0, 0, 2},
+			},
+		},
+		{
+			input:  []int{-3, -2, -1, 0, 0, 1, 2, 3},
+			target: 0,
+			expected: [][]int{
+				{-3, -2, 2, 3},
+				{-3, -1, 1, 3},
+				{-3, 0, 0, 3},
+				{-3, 0, 1, 2},
+				{-2, -1, 0, 3},
+				{-2, -1, 1, 2},
+				{-2, 0, 0, 2},
+				{-1, 0, 0, 1},
+			},
+		},
+		{
+			input:  []int{1, -2, -5, -4, -3, 3, 3, 5},
+			target: -11,
+			expected: [][]int{
+				{-5, -4, -3, 1},
+			},
+		},
+	}
+	for _, tc := range tests {
+		output := fourSum(tc.input, tc.target)
+		if !reflect.DeepEqual(output, tc.expected) {
+			t.Fatalf("input: %v, output: %v, expected: %v", tc.input, output, tc.expected)
+		}
+	}
+}