Merge branch 'master' of https://github.com/cxjwin/go-algocasts

leetcode/leetcode153/find_minimum_in_rotated_sorted_array.go

@@ -0,0 +1,43 @@
+package leetcode153
+
+func findMin(nums []int) int {
+	if nums == nil || len(nums) == 0 {
+		return 0
+	}
+
+	low, high := 0, len(nums)-1
+
+	for low < high {
+		mid := low + (high-low)/2
+		if nums[mid] > nums[high] {
+			low = mid + 1
+		} else {
+			high = mid
+		}
+	}
+
+	return nums[low]
+}
+
+func findMinEarlyReturn(nums []int) int {
+	if nums == nil || len(nums) == 0 {
+		return 0
+	}
+
+	low, high := 0, len(nums)-1
+
+	for low < high {
+		if nums[low] < nums[high] {
+			return nums[low]
+		}
+
+		mid := low + (high-low)/2
+		if nums[mid] > nums[high] {
+			low = mid + 1
+		} else {
+			high = mid
+		}
+	}
+
+	return nums[low]
+}

leetcode/leetcode153/find_minimum_in_rotated_sorted_array_test.go

@@ -0,0 +1,15 @@
+package leetcode153
+
+import "testing"
+
+func TestFindMin(t *testing.T) {
+	type testFunc func([]int) int
+	testBody := func(f testFunc, t *testing.T) {
+		nums := []int{4, 5, 6, 7, 0, 1, 2}
+		if f(nums) != 0 {
+			t.Error("4, 5, 6, 7, 0, 1, 2 -> 0")
+		}
+	}
+	testBody(findMin, t)
+	testBody(findMinEarlyReturn, t)
+}

leetcode/leetcode207/course_schedule.go

@@ -2,7 +2,7 @@ package leetcode207
 
 // https://leetcode.com/problems/course-schedule/
 
-func hasCycle(graph map[int][]int, checked []bool, visited []bool, v int) bool {
+func hasCycle(graph [][]int, checked []bool, visited []bool, v int) bool {
 	if visited[v] {
 		return true
 	}
@@ -16,7 +16,6 @@ func hasCycle(graph map[int][]int, checked []bool, visited []bool, v int) bool {
 	}
 
 	checked[v] = true
-	visited[v] = false
 
 	return false
 }
@@ -26,23 +25,22 @@ func canFinish(numCourses int, prerequisites [][]int) bool {
 		return true
 	}
 
-	m := make(map[int][]int)
+	graph := make([][]int, numCourses)
+	for i := 0; i < numCourses; i++ {
+		graph[i] = make([]int, 0)
+	}
 
-	for _, pair := range prerequisites {
-		arr, ok := m[pair[1]]
-		if !ok {
-			arr = []int{pair[0]}
-		} else {
-			arr = append(arr, pair[0])
-		}
-		m[pair[1]] = arr
+	for _, v := range prerequisites {
+		idx := v[1]
+		val := v[0]
+		graph[idx] = append(graph[idx], val)
 	}
 
 	checked := make([]bool, numCourses)
-	visited := make([]bool, numCourses)
 
 	for i := 0; i < numCourses; i++ {
-		if !checked[i] && hasCycle(m, checked, visited, i) {
+		visited := make([]bool, numCourses)
+		if !checked[i] && hasCycle(graph, checked, visited, i) {
 			return false
 		}
 	}
@@ -55,38 +53,40 @@ func canFinishTopoSort(numCourses int, prerequisites [][]int) bool {
 		return true
 	}
 
-	inDegree := make([]int, numCourses)
-
 	graph := make([][]int, numCourses)
 	for i := 0; i < numCourses; i++ {
 		graph[i] = make([]int, 0)
 	}
 
+	inDegrees := make([]int, numCourses)
 	for _, v := range prerequisites {
+		// set graph
 		arr := graph[v[1]]
 		arr = append(arr, v[0])
 		graph[v[1]] = arr
-		inDegree[v[0]]++
+		// set inDegrees
+		inDegrees[v[0]]++
 	}
 
-	queue := make([]int, 0)
-	for i, v := range inDegree {
+	st := make([]int, 0)
+	for i, v := range inDegrees {
 		if v == 0 {
-			queue = append(queue, i)
+			st = append(st, i)
 		}
 	}
 
 	count := 0
-
-	for len(queue) != 0 {
-		idx := queue[len(queue)-1]
-		queue = queue[:len(queue)-1]
-
+	for len(st) != 0 {
+		// pop
+		idx := st[len(st)-1]
+		st = st[:len(st)-1]
 		count++
-		for _, i := range graph[idx] {
-			inDegree[i]--
-			if inDegree[i] == 0 {
-				queue = append(queue, i)
+
+		arr := graph[idx]
+		for _, v := range arr {
+			inDegrees[v]--
+			if inDegrees[v] == 0 {
+				st = append(st, v)
 			}
 		}
 	}

leetcode/leetcode207/course_schedule_test.go

@@ -2,6 +2,21 @@ package leetcode207
 
 import "testing"
 
+func TestHasCycle(t *testing.T) {
+	input := [][]int{
+		{1},
+		{2},
+		{0},
+	}
+
+	checked := make([]bool, 3)
+	visited := make([]bool, 3)
+	res := hasCycle(input, checked, visited, 0)
+	if !res {
+		t.Error("has cycle")
+	}
+}
+
 func TestCanFinish(t *testing.T) {
 	type testFunc func(int, [][]int) bool
 

leetcode/leetcode210/course_schedule_ii.go

@@ -17,7 +17,6 @@ func hasCycle(graph map[int][]int, checked []bool, visited []bool, order *[]int,
 
 	*order = append(*order, v)
 	checked[v] = true
-	visited[v] = false
 
 	return false
 }
@@ -39,11 +38,11 @@ func findOrder(numCourses int, prerequisites [][]int) []int {
 	}
 
 	checked := make([]bool, numCourses)
-	visited := make([]bool, numCourses)
 	temp := make([]int, 0)
 	res := &temp
 
 	for i := 0; i < numCourses; i++ {
+		visited := make([]bool, numCourses)
 		if !checked[i] && hasCycle(m, checked, visited, res, i) {
 			return []int{}
 		}
@@ -57,3 +56,49 @@ func findOrder(numCourses int, prerequisites [][]int) []int {
 
 	return output
 }
+
+func findOrderTopoSort(numCourses int, prerequisites [][]int) []int {
+	if numCourses <= 1 || prerequisites == nil || len(prerequisites) == 0 {
+		return []int{}
+	}
+
+	graph := make([][]int, numCourses)
+	for i := 0; i < numCourses; i++ {
+		graph[i] = make([]int, 0)
+	}
+
+	inDegrees := make([]int, numCourses)
+	for _, v := range prerequisites {
+		arr := graph[v[1]]
+		arr = append(arr, v[0])
+		graph[v[1]] = arr
+
+		inDegrees[v[0]]++
+	}
+
+	st := make([]int, 0)
+	for _, v := range inDegrees {
+		if v == 0 {
+			st = append(st, v)
+		}
+	}
+
+	output := make([]int, 0)
+
+	for len(st) != 0 {
+		idx := st[len(st)-1]
+		st = st[:len(st)-1]
+
+		output = append(output, idx)
+
+		arr := graph[idx]
+		for _, v := range arr {
+			inDegrees[v]--
+			if inDegrees[v] == 0 {
+				st = append(st, v)
+			}
+		}
+	}
+
+	return output
+}

leetcode/leetcode210/course_schedule_ii_test.go

@@ -6,35 +6,42 @@ import (
 )
 
 func TestFindOrder(t *testing.T) {
-	case1 := [][]int{
-		{1, 0},
-		{3, 0},
-		{3, 1},
-		{2, 1},
-		{2, 3},
-		{4, 2},
-		{4, 3},
-	}
-	if !reflect.DeepEqual(findOrder(5, case1), []int{0, 1, 3, 2, 4}) {
-		t.Error("case1 => 0, 1, 3, 2, 4")
-	}
+	type testFunc func(int, [][]int) []int
 
-	case2 := [][]int{
-		{1, 0},
-	}
-	if !reflect.DeepEqual(findOrder(2, case2), []int{0, 1}) {
-		t.Error("case2 => 0, 1")
-	}
+	testBody := func(f testFunc, t *testing.T) {
+		case1 := [][]int{
+			{1, 0},
+			{3, 0},
+			{3, 1},
+			{2, 1},
+			{2, 3},
+			{4, 2},
+			{4, 3},
+		}
+		if !reflect.DeepEqual(f(5, case1), []int{0, 1, 3, 2, 4}) {
+			t.Error("case1 => 0, 1, 3, 2, 4")
+		}
 
-	case3 := [][]int{
-		{1, 0},
-		{2, 0},
-		{3, 1},
-		{3, 2},
-	}
-	res := findOrder(4, case3)
-	if !reflect.DeepEqual(res, []int{0, 1, 2, 3}) &&
-		!reflect.DeepEqual(res, []int{0, 2, 1, 3}) {
-		t.Error("case3 => 0, 1, 2, 3 or 0, 2, 1, 3")
+		case2 := [][]int{
+			{1, 0},
+		}
+		if !reflect.DeepEqual(f(2, case2), []int{0, 1}) {
+			t.Error("case2 => 0, 1")
+		}
+
+		case3 := [][]int{
+			{1, 0},
+			{2, 0},
+			{3, 1},
+			{3, 2},
+		}
+		res := f(4, case3)
+		if !reflect.DeepEqual(res, []int{0, 1, 2, 3}) &&
+			!reflect.DeepEqual(res, []int{0, 2, 1, 3}) {
+			t.Error("case3 => 0, 1, 2, 3 or 0, 2, 1, 3")
+		}
 	}
+
+	testBody(findOrder, t)
+	testBody(findOrderTopoSort, t)
 }

leetcode/leetcode54/spiral_matrix.go

@@ -0,0 +1,48 @@
+package leetcode54
+
+func spiralOrder(matrix [][]int) []int {
+	if matrix == nil || len(matrix) == 0 || len(matrix[0]) == 0 {
+		return []int{}
+	}
+
+	top, left, bottom, right := 0, 0, len(matrix)-1, len(matrix[0])-1
+
+	res := make([]int, 0)
+
+	for {
+
+		for i := left; i <= right; i++ {
+			res = append(res, matrix[top][i])
+		}
+		top++
+		if top > bottom {
+			break
+		}
+
+		for i := top; i <= bottom; i++ {
+			res = append(res, matrix[i][right])
+		}
+		right--
+		if right < left {
+			break
+		}
+
+		for i := right; i >= left; i-- {
+			res = append(res, matrix[bottom][i])
+		}
+		bottom--
+		if bottom < top {
+			break
+		}
+
+		for i := bottom; i >= top; i-- {
+			res = append(res, matrix[i][left])
+		}
+		left++
+		if left > right {
+			break
+		}
+	}
+
+	return res
+}