This notebook was prepared by Donne Martin. Source and license info is on GitHub.

Solution Notebook

Problem: Assign Cookies.

See the LeetCode problem page.

Assume you are an awesome parent and want to give your children some cookies. But, you should give each child at most one cookie. Each child i has a greed factor gi, which is the minimum size of a cookie that the child will be content with; and each cookie j has a size sj. If sj >= gi, we can assign the cookie j to the child i, and the child i will be content. Your goal is to maximize the number of your content children and output the maximum number.

Note: You may assume the greed factor is always positive. You cannot assign more than one cookie to one child.

Example 1: Input: [1,2,3], [1,1]

Output: 1

Explanation: You have 3 children and 2 cookies. The greed factors of 3 children are 1, 2, 3. And even though you have 2 cookies, since their size is both 1, you could only make the child whose greed factor is 1 content. You need to output 1. Example 2: Input: [1,2], [1,2,3]

Output: 2

Explanation: You have 2 children and 3 cookies. The greed factors of 2 children are 1, 2. You have 3 cookies and their sizes are big enough to gratify all of the children, You need to output 2.

Constraints

  • Are the inputs two list(int), one for greed factor and the other for cookie size?
    • Yes
  • Are the inputs are sorted increasing order?
    • No
  • Can we change inputs themselves, or do we need to make a copy?
    • You can change them
  • Is the output an int?
    • Yes
  • Is the greed factor always >= 1?
    • Yes
  • Can we assume the inputs are valid?
    • No, check for None
  • Can we assume this fits memory?
    • Yes

Test Cases

* None input -> TypeError
[1, 2, 3], [1, 1] -> 1
[1, 2], [1, 2, 3] -> 2
[7, 8, 9, 10], [5, 6, 7, 8] -> 2

Algorithm

  • Sort the inputs
  • We'll keep an index to the current greed factor
  • For each cookie
    • Assign it to a child if its size >= the child's greed factor
      • Increment result counter
      • Increment the index to the greed factor
        • Careful of this index going out of bounds
  • Return the result counter

Complexity:

  • Time: O(n log n) for the sort
  • Space: O(1), assuming the sort is in-place

Code

In [1]:
class Solution(object):

    def find_content_children(self, greed_indices, cookie_sizes):
        if greed_indices is None or cookie_sizes is None:
            raise TypeError('greed_indices or cookie_sizes cannot be None')
        if not greed_indices or not cookie_sizes:
            return 0
        greed_indices.sort()
        cookie_sizes.sort()
        greed_index = 0
        num_children = 0
        for size in cookie_sizes:
            if greed_index >= len(greed_indices):
                break
            if size >= greed_indices[greed_index]:
                num_children += 1
                greed_index += 1
        return num_children

Unit Test

In [2]:
%%writefile test_assign_cookie.py
import unittest


class TestAssignCookie(unittest.TestCase):

    def test_assign_cookie(self):
        solution = Solution()
        self.assertRaises(TypeError, solution.find_content_children, None, None)
        self.assertEqual(solution.find_content_children([1, 2, 3], 
                                                    [1, 1]), 1)
        self.assertEqual(solution.find_content_children([1, 2], 
                                                    [1, 2, 3]), 2)
        self.assertEqual(solution.find_content_children([7, 8, 9, 10], 
                                                    [5, 6, 7, 8]), 2)
        print('Success: test_find_content_children')


def main():
    test = TestAssignCookie()
    test.test_assign_cookie()


if __name__ == '__main__':
    main()
Overwriting test_assign_cookie.py
In [3]:
%run -i test_assign_cookie.py
Success: test_find_content_children