A Combinatorics Problem
Difference between en1 and en2, changed 7 character(s)
Hi,Codeforces! I need your help!↵
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There is an kind of integer sequence of length _(n+k)_. _(k<=n)_↵
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Constraints follow:↵
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1. For every element in sequence, its value is either -1 or a positive integer.↵
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2. The number of -1's occurrences is n and the number of positive integers's occurrences is k.↵
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3. The sum of all positive integers  equals n.↵
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4. Any prefix sum of the sequence is non-negative.↵
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Now you must calculate the number of different sequences satisfying the constraints above.↵
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Is there a general formula for this answer?↵
Most thanks.↵
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  Rev. Lang. By When Δ Comment
en2 English wtw 2017-03-15 18:52:43 7 Tiny change: 'There is an integer s' -> 'There is a kind of integer s'
en1 English wtw 2017-03-15 18:51:24 584 Initial revision (published)