Mock CCO '19 Contest 1 Problem 5 - A Tree Problem - Olympiads Online Judge

Mock CCO '19 Contest 1 Problem 5 - A Tree Problem

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Points: 25 (partial)

Time limit: 0.6s

Memory limit: 162M

Problem types

Count the number of distinct spanning trees that exist on $N$ $N$ labeled vertices, given that some of these vertices are restricted in their degree.

Constraints

$1 \le N \le 1000$ $1 \leq N \leq 1000$

In test data worth 30% of marks, you may assume $N \le 300$ $N \leq 300$ .

Input Specification

The first line contains a single positive integer, $N$ $N$ .

Each of the next $N$ $N$ lines contains a single integer, $d_i$ $d_{i}$ . If $d_i$ $d_{i}$ is -1, then there is no degree restriction on vertex $i$ $i$ . Otherwise, vertex $i$ $i$ must have degree $d_i$ $d_{i}$ .

Output Specification

Output the number of distinct spanning trees.

Sample Input

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3
-1
-1
1

Sample Output

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Comments

14

bqi343 commented on May 19, 2019, 1:52 p.m.

Just read the formula at the end of this link.