9.1.7 Checkerboard V2 Codehs May 2026

This problem is a classic introduction to Nested Loops and Modular Arithmetic. It asks you to draw a checkerboard pattern where the color of each square depends on its position (row and column).

9.1.7: Checkerboard V2 is a fundamental test of your ability to manipulate 2D lists (nested lists) using nested loops and conditional logic. While V1 typically focuses on simple row replacement, V2 requires a precise alternating pattern of 0s and 1s across the entire grid. Core Logic: The Alternating Pattern The primary challenge is ensuring that if a cell at (row, col) is a 1, the adjacent cells (up, down, left, right) are 0s. The Modulus Trick 9.1.7 Checkerboard V2 Codehs

JavaScript Solution (Console – Node.js)

const readline = require('readline');
const rl = readline.createInterface(
    input: process.stdin,
    output: process.stdout
);
The most efficient way to pass the autograder—which often requires specific assignment statements This problem is a classic introduction to Nested
Fix: In programming, grids almost always start at index 0. Use row < 8. x = col * squareSize 
 y = row * squareSize
1. Nested Loops (The Structure)
The core of this problem is the Nested Loop:

x = col * squareSize
y = row * squareSize


A perfect grid of squares.
Alternating colors in a checker pattern.
No gaps or overlaps.
Correct dimensions (e.g., 8×8 squares each 50px = 400px canvas).