t steps to convert char into next nums[c] chars #hard #dp #math


https://leetcode.com/problems/total-characters-in-string-after-transformations-ii/description

https://leetcode.com/problems/painting-a-grid-with-three-different-colors/description


Ways to 3-color m*n grid, no adjucents #hard #dp #matrix

https://leetcode.com/problems/find-the-maximum-sum-of-node-values/description/

Max sum by k-xoring edges #hard #tree #dp