Checklist VsOSh AI 2026 Municipal Stage (Moscow), grades 9–11 · Task 5
Decision Non-Making Tree
Russian title: Дерево непринятия решений
Compute the probabilities of all leaves of a depth-3 probabilistic binary tree and print the leaf codes in sorted order.
The task
A full binary tree of depth n is used like a decision tree: every internal node stores p (0 ≤ p ≤ 100), the probability in percent of going left (0) rather than right (1). Each leaf corresponds to a binary string of length n whose probability is the product of the choices along its path. Dima built a tree of depth 3 with 7 internal nodes arranged as in a figure.
Print all 8 binary strings of length 3 in non-decreasing order of probability, breaking ties lexicographically.
Abridged and translated by SOTA from the official Russian materials. The official statement has the exact rules, and it wins wherever this summary differs.
In English
This task was published in Russian. SOTA translated its 4 files into English on 16 September 2026.
- Task statement Russian original of Task statement
- Official solution Russian original of Official solution
- Full paper (all tasks of the stage) Russian original of Full paper (all tasks of the stage)
- All answers and solutions of the stage Russian original of All answers and solutions of the stage
Read the task statement in English
Decision Non-Making Tree
English translation by SOTA – AI Community of the Russian original. Organisers who would like this translation removed can email [email protected].
Task 5 of the municipal stage (Moscow) of the All-Russian School Olympiad (VsOSh) 2025/26 in artificial intelligence, grades 9–11 (variant III). Original: tasks-ai-9-11-mun-msk-25-26.pdf.
Time limit: 1 second
Memory limit: 256 megabytes
Decision trees are often used in machine learning. Each internal vertex of such a tree corresponds to some question, and each edge corresponds to the choice of an answer (yes/no). In this way, with a few questions, the input data can be split into a fairly large number of classes. Dima's latest project is a decision non-making tree. Its structure is similar to that of a decision tree. It is a complete binary tree of depth . Every vertex, except the vertices of the last level, stores a number (). This number is the probability of the choice: with probability per cent the algorithm chooses to go left and, accordingly, with probability per cent it goes right.
Let us agree to denote a move to the left by the digit 0 and a move to the right by the digit 1. Thus, each vertex of the bottom level corresponds to a binary string of length (the sequence of decisions from the root to the leaf).
The probability of obtaining this string equals the product of the probabilities of all the choices made on the path from the root to the leaf.
Dima has already written a structure for such a tree and wants to test it. For this, he created a tree of depth 3. So it has 7 internal vertices in total. Each vertex has its own number . The layout of these vertices is shown below:
[Figure: the layout of the vertices; see page 2 of the original PDF. Transcription: internal vertices 1–7, edges labelled 0 (left) and 1 (right), leaves labelled with their binary strings.]
(1)
0 / \ 1
(2) (3)
0 / \ 1 0 / \ 1
(4) (5) (6) (7)
0/ \1 0/ \1 0/ \1 0/ \1
000 001 010 011 100 101 110 111
Find the probabilities of all binary strings of length 3 and output the strings in non-decreasing order of probability. If probabilities are equal, the strings must be output in lexicographic order.
Input format
The first line contains 7 integers (): the probabilities for the vertices, as shown in the figure.
Output format
Output 8 lines. Each line must contain a binary string of length 3. The strings must be in non-decreasing order of probability. If probabilities are equal, the strings are compared lexicographically.
Examples
Standard input:
40 90 20 90 100 70 0
Standard output:
011
110
001
101
010
100
000
111
Note
In the first test example, the binary strings have the following probabilities:
- 011 – 0.0
- 110 – 0.0
- 001 – 0.036
- 101 – 0.036
- 010 – 0.04
- 100 – 0.084
- 000 – 0.324
- 111 – 0.48
Scoring criterion: exact match of the answer — 100 points
Maximum score for the task — 100
Translated by SOTA. The Russian original is the official version and wins wherever the two differ. Translated from the statement and answer PDFs of the Moscow municipal stage (grades 9–11) on vos.olimpiada.ru. The figure of the tree is transcribed as a text diagram, with a link to the original page. If you organise this olympiad and would like the translation removed, email [email protected] and we will take it down.
At a glance
- You get
- Standard input: 7 integers p (0 ≤ p ≤ 100) for the nodes in the order shown in the figure.
- You submit
- Eight lines, each a binary string of length 3.
- Scoring
- Exact match of the output; 100 points maximum.
- Rules
- Time limit 1 s; memory limit 256 MB.
- Format
- Municipal stage (Moscow), 17 December 2025, grades 9–11; individual; 180 minutes; answers and programs submitted to an online testing system; maximum 600 points for the paper.