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ICPC 2011
ICPC 2011

C. Ancient Messages

Problem ID: ancient In order to understand early civilizations, archaeologists often study texts written in ancient languages. One such language, used in Egypt more than 3000 years ago, is based on characters called hieroglyphs. Figure C.1 shows six hierogl...

Updated May 21, 2026
Track ICPC
Year 2011
Statement Text + PDF
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Problem statement

Problem Statement

Formatted from the contest statement text, with sample tests broken out into copyable blocks.

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In order to understand early civilizations, archaeologists often study texts written in ancient languages. One such language, used in Egypt more than 3000 years ago, is based on characters called hieroglyphs. Figure C.1 shows six hieroglyphs and their names. In this problem, you will write a program to recognize these six characters.

Ankh Wedjat Djed Scarab Was Akeht

Figure C.1: Six hieroglyphs

Input

The input consists of several test cases, each of which describes an image containing one or more hieroglyphs chosen from among those shown in Figure C.1. The image is given in the form of a series of horizontal scan lines consisting of black pixels (represented by 1) and white pixels (represented by 0). In the input data, each scan line is encoded in hexadecimal notation. For example, the sequence of eight pixels 10011100 (one black pixel, followed by two white pixels, and so on) would be represented in hexadecimal notation as 9c. Only digits and lowercase letters a through f are used in the hexadecimal encoding. The first line of each test case contains two integers, H and W. H (0 < H ≤ 200) is the number of scan lines in the image. W (0 < W ≤ 50) is the number of hexadecimal characters in each line. The next H lines contain the hexadecimal characters of the image, working from top to bottom. Input images conform to the following rules:

  • The image contains only hieroglyphs shown in Figure C.1.
  • Each image contains at least one valid hieroglyph.
  • Each black pixel in the image is part of a valid hieroglyph.
  • Each hieroglyph consists of a connected set of black pixels and each black pixel has at least one other black pixel on its top, bottom, left, or right side.
  • The hieroglyphs do not touch and no hieroglyph is inside another hieroglyph.
  • Two black pixels that touch diagonally will always have a common touching black pixel.
  • The hieroglyphs may be distorted but each has a shape that is topologically equivalent to one of the symbols in Figure C.11 .

The last test case is followed by a line containing two zeros.

1 Two figures are topologically equivalent if each can be transformed into the other by stretching without tearing.

ICPC 2011 World Finals Problem C: Ancient Messages

Output

For each test case, display its case number followed by a string containing one character for each hieroglyph recognized in the image, using the following code:

Ankh: A
Wedjat: J
Djed: D
Scarab: S
Was: W
Akhet: K

In each output string, print the codes in alphabetic order. Follow the format of the sample output. The sample input contains descriptions of test cases shown in Figures C.2 and C.3. Due to space constraints not all of the sample input can be shown on this page.

Figure C.2: AKW                                                Figure C.3: AAAAA

Sample Tests

Sample
Sample Input 
  100 25
  0000000000000000000000000
  0000000000000000000000000
   ...(50 lines omitted)...
  00001fe0000000000007c0000
  00003fe0000000000007c0000
   ...(44 lines omitted)...
  0000000000000000000000000
  0000000000000000000000000
  150 38
  00000000000000000000000000000000000000
  00000000000000000000000000000000000000
      ...(75 lines omitted)...
  0000000003fffffffffffffffff00000000000
  0000000003fffffffffffffffff00000000000
      ...(69 lines omitted)...
  00000000000000000000000000000000000000
  00000000000000000000000000000000000000
  0 0

ICPC 2011 World Finals Problem C: Ancient Messages
Sample Output 
Case 1: AKW
Case 2: AAAAA
Editorial

Editorial

The solution write-up is rendered from the LaTeX source, with equations kept live through MathJax.

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Key Observations

  • Write the structural observations that make the problem tractable.

  • State any useful invariant, monotonicity property, graph interpretation, or combinatorial reformulation.

  • If the constraints matter, explain exactly which part of the solution they enable.

Algorithm

  1. Describe the data structures and the state maintained by the algorithm.

  2. Explain the processing order and why it is sufficient.

  3. Mention corner cases explicitly if they affect the implementation.

Correctness Proof

We prove that the algorithm returns the correct answer.

Lemma 1.

State the first key claim.

Proof.

Provide a concise proof.

Lemma 2.

State the next claim if needed.

Proof.

Provide a concise proof.

Theorem.

The algorithm outputs the correct answer for every valid input.

Proof.

Combine the lemmas and finish the argument.

Complexity Analysis

State the running time and memory usage in terms of the input size.

Implementation Notes

  • Mention any non-obvious implementation detail that is easy to get wrong.

  • Mention numeric limits, indexing conventions, or tie-breaking rules if relevant.

Implementation

Code

C++ solution used for this page.

C++

Clean code view with a raw-file link when you want the original source.

Raw file 
#include <bits/stdc++.h>
using namespace std;

namespace {

void solve() {
    // Fill in the full solution logic for the problem here.
}

}  // namespace

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    solve();
    return 0;
}
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