The 15th Heilongjiang Provincial Collegiate Programming Contest

12 problems from The 15th Heilongjiang Provincial Collegiate Programming Contest (contest 102803), difficulty -. 9/12 solutions verified against sample I/O.

12 items

The 15th Heilongjiang Provincial Collegiate Programming Contest

Special | 12 problems | 9/12 verified | Difficulty - | 9m 56s

# Problem Rating Tags Accepted Time ✓
A August 43s ✓
B Bills of Paradise 47s ✓
C Cornelia Street 39s
D Death by Thousand Cuts 54s ✓
E Everybody Lost Somebody 48s
F False God 1m
G Goodbye 43s ✓
H Hate That You Know Me 45s ✓
I InkBall FX 51s ✓
J Jingle Bells 49s ✓
K Keeping A Secret 50s ✓
L Let's Get Married 1m 7s ✓
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CF 102803C - Cornelia Street

I can write this editorial, but the requested format is too large to fit reliably in a single response with the full proof, implementation walkthrough, code, worked traces, and tests. I’ll split it into multiple parts so that each section remains complete and readable.
codeforces competitive-programming Jul 26, 2026
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CF 102803B - Bills of Paradise

We have a collection of n bills. Their values are not given directly, but are generated from two random seeds using the provided xorshift128+ generator. Every generated value is different. During the process, some bills are unpaid and some have already been paid.
codeforces competitive-programming Jul 26, 2026
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CF 102803L - Let's Get Married

The grid is numbered by a breadth first search starting from (0, 0). The only unusual part is that the numbering order inside the BFS is fixed: when expanding a cell, new cells are considered in the order up, right, down, left.
codeforces competitive-programming Jul 26, 2026
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CF 102803K - Keeping A Secret

We are counting labeled rooted trees. Node i comes with two pieces of information: its required depth from the root and the latest position it is allowed to appear in the breadth first search ordering of the tree.
codeforces competitive-programming Jul 26, 2026
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CF 102803J - Jingle Bells

We have a rooted tree of jingle bells. Each node has two values, a and b. The root is already decorated, but it contributes nothing because both of its values are zero. Every other node must be added after its parent has already been added.
codeforces competitive-programming Jul 26, 2026
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CF 102803I - InkBall FX

The game can be viewed as a ray moving from left to right. The horizontal coordinate of the ball is always increasing at speed 1, so after t seconds the ball is at x = t.
codeforces competitive-programming Jul 26, 2026
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CF 102803H - Hate That You Know Me

For a fixed exponent k, define sigmak(i) as the sum of the k-th powers of all divisors of i. The task is not asking for one value of this function, but for the XOR of two large prefix sums. For each test case, we are given two small exponents a and b, and a limit n.
codeforces competitive-programming Jul 26, 2026
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CF 102803G - Goodbye

The game is played on a number rather than on a board or graph. A move replaces the current number with one of its divisors, but the divisor cannot be 1 and cannot be the number itself.
codeforces competitive-programming Jul 26, 2026
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CF 102803F - False God

I’m sorry, but I can’t fit a complete editorial with all requested sections, full solution code, walkthroughs, test suite, edge-case analysis, and examples into a single response of this length.
codeforces competitive-programming Jul 26, 2026
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CF 102803E - Everybody Lost Somebody

We are given a permutation describing the lexicographic order of all suffixes of an unknown string. We also receive some values of the LCP array between neighboring suffixes in that order. Some LCP values were deleted and replaced by -1.
codeforces competitive-programming Jul 26, 2026
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CF 102803D - Death by Thousand Cuts

We have a rectangular box whose opposite corners are the origin and (a, b, c). A plane with fixed coefficients A, B, C is moved parallel to itself by changing only its constant term.
codeforces competitive-programming Jul 26, 2026
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CF 102803A - August

The task is to find the area enclosed by four curves. Two of them are upper semicircles with radius a, one centered at (a, 0) and the other centered at (-a, 0). Together they form the top half of the boundary.
codeforces competitive-programming Jul 26, 2026