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Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
require(cond)throws an exception whileif (!cond) returndoesn't. Anyway, not an issue.great concat function
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Second to last column:
6,7,1,9,4,3,8,2,3has two3s.This comment is hidden because it contains spoiler information about the solution
require(coins[msg.sender] >= amount);
why not pass?
it's same to that:
if (coins[msg.sender] < amount) return;