## Editorial for DMOPC '14 Exam Time P6 - Math Homework

Remember to use this editorial

**only**when stuck, and**not to copy-paste code from it**. Please be respectful to the problem author and editorialist.**Submitting an official solution before solving the problem yourself is a bannable offence.**Author:

Since the source was mentioned in the footer, you can Google `HDU 5155 solution`

for some initial ideas. However, the given solutions are all too slow — or . To speed it up, you can assume each row has at least one `1`

( ways to do so) and either use the Inclusion-Exclusion Principle or dynamic programming with the binomial coefficient to compute the ways with rows and columns for .

**Time complexity:** or

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