Hello, I was solving golf from JOI 2017 Open. I tested in polygon with author's solution. My solution got WA, then I decided to change C++17 to C++14 and magically I've got AC. Can someone tell me how is that possible. Also I submitted it to oj.uz where compiler is under Ubuntu and it also gives wrong answer code test
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Codeforces (c) Copyright 2010-2024 Михаил Мирзаянов
Соревнования по программированию 2.0
Время на сервере: 17.05.2024 04:33:56 (k2).
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I changed links to array, still doesn't work. code
Undefined behaviour or bug in g++. It's so obvious.
So why UD should work in other compilers than C++17
It's not really that it "works" in C++14, it just happened to not fail. You know, because it's undefined behavior.
Not to fail in 50 tests? Seems quite strange to me.
You are yellow, was red, and act like a green. You are able to handle this thing by yourself.
If I was able to, I wouldn't ask to help me. This is too hard for "yellow".
Line 255-256:
Sometimes upper_bound returns st.begin() causing undefined behavior when you decrement the iterator. Did you even try to test for UB before you made a codeforces blog to cry about C++17?
Why are you so mad, not everyone so smart like you. I never heard that upper_bound can return begin. Also I inserted -1 and inf some lines above and I can't remove them.
Yes you did. You inserted -1 above.And then you proceeded to check for -inf. Inserting -1 literally does nothing. If you insert -inf then it outputs the correct answer.
"I never heard that upper_bound can return begin". I actually wonder how you were once red...
Values that I use for upper and lower bound are in range 0..2*n+2, I use -inf for removing elements and inf to inserting elements as you can see.
Oh, actually I understood what you meant with upper_bound returning begin, I thought if there is no element instead of end it returns begin. Haha :D Anyway it can't happen, you can set assert if you don't believe.
Is 10 the correct answer to test?
8 Is the correct answer.
If someone was wondering what was the problem. I found bug, actually in Windows C++14 and earlier when you access element of map, it creates if wasn't firstly. I was using it to compress values on lines 216-217. So in Windows elements started from 0, and in Linux from -1.