added problem 2050

Author: SHA65536

problems/problem2050/parallel_courses_iii.go

@@ -0,0 +1,64 @@
+package problem2050
+
+/*
+You are given an integer n, which indicates that there are n courses labeled from 1 to n.
+You are also given a 2D integer array relations where relations[j] = [prevCoursej, nextCoursej] denotes that
+course prevCoursej has to be completed before course nextCoursej (prerequisite relationship).
+Furthermore, you are given a 0-indexed integer array time where time[i] denotes
+how many months it takes to complete the (i+1)th course.
+You must find the minimum number of months needed to complete all the courses following these rules:
+You may start taking a course at any time if the prerequisites are met.
+Any number of courses can be taken at the same time.
+Return the minimum number of months needed to complete all the courses.
+Note: The test cases are generated such that it is possible to complete every course
+(i.e., the graph is a directed acyclic graph).
+*/
+
+func minimumTime(n int, relations [][]int, time []int) int {
+	var res int
+	// graph[i] represents the courses the i'th course needs
+	var graph = make([][]int, n)
+	// fTime[i] represesnts the minimal time needed to complete the i'th course
+	var fTime = make([]int, n)
+	// solve(i) recursively finds the minimal time to complete the i'th course
+	var solve func(int) int
+
+	// Building the dependency graph
+	for _, r := range relations {
+		graph[r[1]-1] = append(graph[r[1]-1], r[0]-1)
+	}
+
+	solve = func(cur int) int {
+		var res int
+		// If we already found the minimal time, return it
+		if fTime[cur] != 0 {
+			return fTime[cur]
+		}
+
+		// Loop over all the course's dependencies
+		for _, d := range graph[cur] {
+			// Find out their minimal completion time
+			dTime := solve(d)
+			// Pick the maximum of those times, since you need to finish all of them
+			if dTime > res {
+				res = dTime
+			}
+		}
+
+		// Write to cache
+		fTime[cur] = res + time[cur]
+		return fTime[cur]
+	}
+
+	// Loop over all the courses
+	for i := range fTime {
+		// Find the minimal time for each
+		solve(i)
+		// Pick the maximum time (the last course that needs to be completed)
+		if fTime[i] > res {
+			res = fTime[i]
+		}
+	}
+
+	return res
+}

problems/problem2050/parallel_courses_iii_test.go

@@ -0,0 +1,38 @@
+package problem2050
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type TestCase struct {
+	N         int
+	Relations [][]int
+	Time      []int
+	Expected  int
+}
+
+var TestCases = []TestCase{
+	{3, [][]int{{1, 3}, {2, 3}}, []int{3, 2, 5}, 8},
+	{5, [][]int{{1, 5}, {2, 5}, {3, 5}, {3, 4}, {4, 5}}, []int{1, 2, 3, 4, 5}, 12},
+}
+
+func TestParallelCoursesIII(t *testing.T) {
+	assert := assert.New(t)
+
+	for _, tc := range TestCases {
+		want := tc.Expected
+		got := minimumTime(tc.N, tc.Relations, tc.Time)
+		assert.Equal(want, got, fmt.Sprintf("%+v", tc))
+	}
+}
+
+func BenchmarkVParallelCoursesIII(b *testing.B) {
+	for _, tc := range TestCases {
+		for i := 0; i < b.N; i++ {
+			minimumTime(tc.N, tc.Relations, tc.Time)
+		}
+	}
+}

readme.md

@@ -533,6 +533,7 @@ Each problem is in it's own directory, with test files. There are helper package
 | 2017 | [Grid Game](https://leetcode.com/problems/grid-game) | [My Solution](./problems/problem2017) | ✅ |
 | 2024 | [Maximize the Confusion of an Exam](https://leetcode.com/problems/maximize-the-confusion-of-an-exam) | [My Solution](./problems/problem2024) | ✅ |
 | 2038 | [Remove Colored Pieces if Both Neighbors are the Same Color](https://leetcode.com/problems/remove-colored-pieces-if-both-neighbors-are-the-same-color) | [My Solution](./problems/problem2038) | ✅ |
+| 2050 | [Parallel Courses III](https://leetcode.com/problems/parallel-courses-iii) | [My Solution](./problems/problem2050) | ✅ |
 | 2070 | [Most Beautiful Item for Each Query](https://leetcode.com/problems/most-beautiful-item-for-each-query) | [My Solution](./problems/problem2070) | ✅ |
 | 2090 | [K Radius Subarray Averages](https://leetcode.com/problems/k-radius-subarray-averages) | [My Solution](./problems/problem2090) | ✅ |
 | 2095 | [Delete the Middle Node of a Linked List](https://leetcode.com/problems/delete-the-middle-node-of-a-linked-list) | [My Solution](./problems/problem2095) | ✅ |