6cfd0fc503
* fix: improve Project Euler descriptions and test case Improve formatting of Project Euler test descriptions. Also add poker hands array and new test case for problem 54 * feat: add typeof tests and gave functions proper names for first 100 challenges * fix: continue fixing test descriptions and adding "before test" sections * fix: address review comments * fix: adjust grids in 18 and 67 and fix some text that reference files rather than the given arrays * fix: implement bug fixes and improvements from review * fix: remove console.log statements from seed and solution
1.6 KiB
1.6 KiB
id, challengeType, title, forumTopicId
| id | challengeType | title | forumTopicId |
|---|---|---|---|
| 5900f37b1000cf542c50fe8e | 5 | Problem 15: Lattice paths | 301780 |
Description
Starting in the top left corner of a 2×2 grid, and only being able to move to the right and down, there are exactly 6 routes to the bottom right corner.
How many such routes are there through a given gridSize?
Instructions
Tests
tests:
- text: <code>latticePaths(4)</code> should return a number.
testString: assert(typeof latticePaths(4) === 'number');
- text: <code>latticePaths(4)</code> should return 70.
testString: assert.strictEqual(latticePaths(4), 70);
- text: <code>latticePaths(9)</code> should return 48620.
testString: assert.strictEqual(latticePaths(9), 48620);
- text: <code>latticePaths(20)</code> should return 137846528820.
testString: assert.strictEqual(latticePaths(20), 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;
}