Step through the algorithm visually — use Play or the step buttons (inspired by AlgoMaster / visualgo).
Snap 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.
Trapping Rain Water — Snap 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).
0 1 0 2 1 0 1 3 2 1 2 1
6
| Test | Status | Details |
|---|
Ready — edit the code above and click Run or Submit.
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);
}
}Try solving on your own first, then reveal the official answer.