Solve 'Two Sum'

Author: obalunenko

two-sum/spec.md

@@ -0,0 +1,16 @@
+# 1. Two Sum
+
+<https://leetcode.com/problems/two-sum/>
+
+Given an array of integers, return indices of the two numbers such that they add up to a specific target.
+
+You may assume that each input would have exactly one solution, and you may not use the same element twice.
+
+Example:
+
+```text
+Given nums = [2, 7, 11, 15], target = 9,
+
+Because nums[0] + nums[1] = 2 + 7 = 9,
+return [0, 1].
+```

two-sum/sum.go

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+package twosum
+
+func twoSum(nums []int, target int) []int {
+	length := len(nums)
+	if length == 0 {
+		return nil
+	}
+	if length == 1 {
+		if nums[0] == target {
+			return []int{0}
+		}
+	}
+
+	for i := 0; i < length; i++ {
+		a := nums[i]
+		for j := i + 1; j < length; j++ {
+			b := nums[j]
+
+			sum := a + b
+
+			if sum == target {
+				return []int{i, j}
+			}
+		}
+	}
+
+	return nil
+}

two-sum/sum_test.go

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+package twosum
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_twoSum(t *testing.T) {
+	type args struct {
+		nums   []int
+		target int
+	}
+
+	tests := []struct {
+		name string
+		args args
+		want []int
+	}{
+		{
+			name: "sum exist",
+			args: args{
+				nums:   []int{2, 7, 11, 15},
+				target: 9,
+			},
+			want: []int{0, 1},
+		},
+		{
+			name: "empty slice",
+			args: args{
+				nums:   nil,
+				target: 9,
+			},
+			want: nil,
+		},
+		{
+			name: "one element",
+			args: args{
+				nums:   []int{9},
+				target: 9,
+			},
+			want: []int{0},
+		},
+		{
+			name: "no target sum",
+			args: args{
+				nums:   []int{9,2,99},
+				target: 1000,
+			},
+			want: nil,
+		},
+		{
+			name: "3,2,4",
+			args: args{
+				nums:   []int{3,2,4},
+				target: 6,
+			},
+			want: []int{1,2},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := twoSum(tt.args.nums, tt.args.target)
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}