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array of vector is faster than vector of vector for storing adjaceny list?

Revision en2, by diradon, 2020-06-15 19:32:50

Hi all, I recently came across an issue that I am unable to comprehend. While solving problem 1337C, I used the same code twice except using a vector<vector<int> > adj(n) in 83595937 and vector<int> a[n] in 83693762. For some reason, the first submission timed out and the second one passed. I thought maybe it has something to do with the fact that vectors aren't preallocating the proper space but that shouldn't be the case as I am mentioning the size n while declaring the vector of vector as well. I searched for this problem on the internet but the discussion is almost always about vector vs arrays and not 2D containers. Thanks for the help!

EDIT: it's solved! Thanks to vipinkumar17 for pointing it out. Passing vvi as reference fixed the problem: 83860879

Tags 2d vector, #array, #tle, speed

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en2 English diradon 2020-06-15 19:32:50 158
en1 English diradon 2020-06-15 19:13:58 756 Initial revision (published)