Grids and Graphs

The Wells Fargo aptitude test stays inside arrays, strings, and hashing. The interview rounds that follow it do not. Candidates coming through the campus pipeline report a live technical round with a grid on the shared screen. The interviewer draws it, then asks a traversal question. Count a Premium question in a map of land and water. Or watch something spread across a matrix and say how long it takes. A grid is a graph with the edges left implicit, so these are graph problems wearing a plain coat.

Four shapes cover the ground here. A flood fill that visits one connected region at a time and counts how many regions there are. A breadth-first sweep that starts from many sources at once and measures distance in whole steps. A heap of fixed size k that surfaces the kth largest value without sorting everything. And a sorted pass that folds overlapping intervals into one. Learn the four cold and the live rounds hold few surprises.