Matrix interview questions

Rotate an n×n matrix 90 degrees clockwise and return the result as a new array.

Find the area of the largest all-ones square in a binary matrix, where each cell's square size is one more than the smallest of its top, left, and top-left neighbors.

Find the cheapest path from the top-left to the bottom-right of a grid, moving only right or down, by summing each cell with the smaller of the two ways to reach it.

Search a matrix whose rows and columns are both sorted by walking a staircase from the top-right corner, eliminating a whole row or column at each step.

Place N queens on an N×N board so none attack another — a classic backtracking search that places one queen per row and prunes column and diagonal conflicts.

Fill a 9×9 Sudoku grid by backtracking — try each digit in the next empty cell, checking its row, column, and 3×3 box, and undo on a dead end.