Assign Cookies

Problem

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.

Solution

public class Solution {
    public int findContentChildren(int[] g, int[] s) {
        Arrays.sort(g);
        Arrays.sort(s);
        int childIndex = 0;//We need to return this as our result, so init outside the loop
        for (int cookieIndex = 0; cookieIndex < s.length && childIndex < g.length; cookieIndex++) {
            if (s[cookieIndex] >= g[childIndex]) childIndex++;
        }
        return childIndex;
    }
}

Analysis

An easy greedy problem with typical and straightforward greedy solution
We need to distribute cookies to children, so we loop through the cookies
But to make this solution work, we need to sort both arrays
Then if a child is satisfied (cookies[cookieIndex] >= children[childIndex]), we move to next child
Because we cannot assign more than one type of cookie to one child, this greedy solution works
At the end, return the childIndex as our result

Analysis

• Time: O(nlgn), because of using sort() method
• Space: O(1), only constant space is used