Trapping Rain Water

Hard 40 pts New · no attempts yet csharp

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Trapping Rain Water — Hexaware interview prep · Two Pointers

Classic interview problem #42.

Input (stdin)

Line 1: bar heights

Output (stdout)

Total trapped water units

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

Examples

Sample

Input

0 1 0 2 1 0 1 3 2 1 2 1

Output

Static hints

Input format: Line 1: bar heights
DSA Interview 150 — Two Pointers
Problem #42
Frequently asked at Hexaware
Two Pointers

Toolliyo Coach

Stuck? Get a nudge — not the answer

Progressive help: Nudge → Guide → Approach. Full solution stays behind the Solution tab.

Your solution

Editor is open — no login wall to practice.

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.

Official 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();
int l = 0, r = h.Length - 1, lm = 0, rm = 0, water = 0;
while (l < r) {
    if (h[l] < h[r]) { lm = Math.Max(lm, h[l]); water += lm - h[l]; l++; }
    else { rm = Math.Max(rm, h[r]); water += rm - h[r]; r--; }
}
Wi(water);
    }
}

Prefer Coach (Nudge → Guide → Approach) before revealing. No forced signup.

Explanation

Step 1 / 1

Hexaware interview context: Trapping Rain Water is a Hard Two Pointers problem — Shrink the search space from both ends; works on sorted arrays and palindromes.

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

Pattern: Two Pointers

Read from stdin, write to stdout. Classic interview problem #42.

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