Course Schedule

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LinkedIn interview context: Course Schedule is a Medium Graphs problem — BFS for shortest path in unweighted graphs; DFS for connectivity and cycles.

Use the animation above to step through each move before writing code.

Pattern: Graphs

Read from stdin, write to stdout. Classic interview problem #207.

Problem

Course Schedule — LinkedIn interview prep · Graphs

Classic interview problem #207.

Input (stdin)

Line 1: numCourses\nLine 2: numEdges\nNext: a b edges

Output (stdout)

true if can finish all courses

Your program must read from stdin and write the answer to stdout (no extra debug text).

Examples

Sample

Input

2
1
1 0

Output

true

Hints

Input format: Line 1: numCourses\nLine 2: numEdges\nNext: a b edges
DSA Interview 150 — Graphs
Problem #207
Frequently asked at LinkedIn
Graphs

Your solution

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class Program
{
    static int[] Ria(string line = null)
    {
        line ??= Console.ReadLine();
        if (string.IsNullOrWhiteSpace(line)) return Array.Empty<int>();
        return line.Trim().Split(new[] { ' ', ',', '\t' }, StringSplitOptions.RemoveEmptyEntries)
            .Select(int.Parse).ToArray();
    }
    static string[] Rsa()
    {
        int n = int.Parse(Console.ReadLine());
        var arr = new string[n];
        for (int i = 0; i < n; i++) arr[i] = Console.ReadLine();
        return arr;
    }
    static void W(params object[] parts) => Console.WriteLine(string.Join(" ", parts));
    static void Wb(bool v) => Console.WriteLine(v ? "true" : "false");
    static void Wi(int v) => Console.WriteLine(v);
    static void Ws(string v) => Console.WriteLine(v);

static void Main()
    {
        // Read from stdin (see problem statement for format)
        // Line 1: numCourses\nLine 2: numEdges\nNext: a b edges

}
}

Ready — edit the code above and click Run or Submit.

Solution

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class Program
{
    static int[] Ria(string line = null)
    {
        line ??= Console.ReadLine();
        if (string.IsNullOrWhiteSpace(line)) return Array.Empty<int>();
        return line.Trim().Split(new[] { ' ', ',', '\t' }, StringSplitOptions.RemoveEmptyEntries)
            .Select(int.Parse).ToArray();
    }
    static string[] Rsa()
    {
        int n = int.Parse(Console.ReadLine());
        var arr = new string[n];
        for (int i = 0; i < n; i++) arr[i] = Console.ReadLine();
        return arr;
    }
    static void W(params object[] parts) => Console.WriteLine(string.Join(" ", parts));
    static void Wb(bool v) => Console.WriteLine(v ? "true" : "false");
    static void Wi(int v) => Console.WriteLine(v);
    static void Ws(string v) => Console.WriteLine(v);

    static void Main()
    {
int n = int.Parse(Console.ReadLine());
int m = int.Parse(Console.ReadLine());
var adj = new List<int>[n];
for (int i = 0; i < n; i++) adj[i] = new List<int>();
for (int i = 0; i < m; i++) {
    var e = Ria();
    adj[e[1]].Add(e[0]);
}
var indeg = new int[n];
foreach (var list in adj) foreach (var v in list) indeg[v]++;
var q = new Queue<int>();
for (int i = 0; i < n; i++) if (indeg[i] == 0) q.Enqueue(i);
int seen = 0;
while (q.Count > 0) {
    int u = q.Dequeue(); seen++;
    foreach (var v in adj[u]) if (--indeg[v] == 0) q.Enqueue(v);
}
Wb(seen == n);
    }
}

Try solving on your own first, then reveal the official answer.

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