Largest Rectangle in Histogram

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Wix interview context: Largest Rectangle in Histogram is a Hard Stack problem — Monotonic stack or bracket matching — watch for O(n) single-pass solutions.

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Pattern: Stack

Read from stdin, write to stdout. Classic interview problem #84.

Problem

Largest Rectangle in Histogram — Wix interview prep · Stack

Classic interview problem #84.

Input (stdin)

Line 1: bar heights

Output (stdout)

Largest rectangle area

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

Examples

Sample

Input

2 1 5 6 2 3

Output

Hints

Input format: Line 1: bar heights
DSA Interview 150 — Stack
Problem #84
Frequently asked at Wix
Stack

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: bar heights

}
}

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()
    {
var h = Ria();
var st = new Stack<int>();
int best = 0;
for (int i = 0; i <= h.Length; i++) {
    int cur = i < h.Length ? h[i] : 0;
    while (st.Count > 0 && cur < h[st.Peek()]) {
        int height = h[st.Pop()];
        int width = st.Count == 0 ? i : i - st.Peek() - 1;
        best = Math.Max(best, height * width);
    }
    st.Push(i);
}
Wi(best);
    }
}

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

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