Centroid / Separator Decomposition
Resource:
https://www.youtube.com/watch?v=LqHAS5EPg1A&list=PLv0QPiaV6CZsUiM0fa0WDLOUiio9jxvfB&fbclid=IwAR0NXQxVJJ1_FlONBoXFITZMlFEu70yPeHkSulghAldHGuBQ5Lc-qRzG8V8
https://www.quora.com/q/threadsiiithyderabad/Centroid-Decomposition-of-a-Tree?fbclid=IwAR0F5yt8vdociDQH2Qc3-R-IW1Kh6yR__dGinIEYUDa3EPHYUQXVxh82-Z4
https://sai16vicky.wordpress.com/2014/11/01/divide-and-conquer-on-trees-centroid-decomposition/?fbclid=IwAR3J92Y3UVkxi-SoECmIf2LevgYswONN-w4VADVkm2ghuYu1x8nDw86lF4A
https://codeforces.com/blog/entry/19175?fbclid=IwAR0wkAhqOLk6gHRJwIITiLPsj0Nv3zY7xE5d5MYh76C_HBYdqZgrI4wF3yE
https://ideone.com/EuKp1v?fbclid=IwAR0YNxRaz0ZdMjwKYXucqVbMWISe3I-_DqhVxF-iMZ-RdBw8WnAVd2Q2ivE
Practice:
https://codeforces.com/problemset/problem/321/C
https://codeforces.com/problemset/problem/161/D
https://codeforces.com/problemset/problem/342/E
https://www.spoj.com/problems/QTREE5/en/
Codeforces Round 937 Div 4 Solution Discussion (with myself) + Answering Your Questions