1.6 KiB
1.6 KiB
id | challengeType | title |
---|---|---|
5900f37b1000cf542c50fe8e | 5 | Problem 15: Lattice paths |
Description
How many such routes are there through a given gridSize
?
Instructions
Tests
tests:
- text: <code>latticePaths(4)</code> should return 70.
testString: assert.strictEqual(latticePaths(4), 70, '<code>latticePaths(4)</code> should return 70.');
- text: <code>latticePaths(9)</code> should return 48620.
testString: assert.strictEqual(latticePaths(9), 48620, '<code>latticePaths(9)</code> should return 48620.');
- text: <code>latticePaths(20)</code> should return 137846528820.
testString: assert.strictEqual(latticePaths(20), 137846528820, '<code>latticePaths(20)</code> should return 137846528820.');
Challenge Seed
function latticePaths(gridSize) {
// Good luck!
return true;
}
latticePaths(4);
Solution
function latticePaths(gridSize) {
let paths = 1;
for (let i = 0; i < gridSize; i++) {
paths *= (2 * gridSize) - i;
paths /= i + 1;
}
return paths;
}