Leetcode #904. Fruit Into Baskets Java Solution and Explanation | Google Interview Question

This is a well-known Google interview question. This seemingly simple problem has many different test cases, edge cases and “gotchas.” I find it to be a great exercise in arrays, pointers and general logic. There are no fancy data structures, dynamic programming, or algebraic formulas involved—just pure logic.

Fruit baskets. Source

Problem

In a row of trees, the i-th tree produces fruit with type tree[i].

You start at any tree of your choice, then repeatedly perform the following steps:

1. Add one piece of fruit from this tree to your baskets. If you cannot, stop.
2. Move to the next tree to the right of the current tree. If there is no tree to the right, stop.

Note that you do not choose after the initial choice of starting tree: you must perform step 1, then step 2, then back to step 1, then step 2, and so on until you stop.

You have two baskets, and each basket can carry any quantity of fruit, but you want each basket only to carry one type of fruit each.

What is the total amount of fruit you can collect with this procedure?

Example 1:

Input: [1,2,1]
Output: 3
Explanation: We can collect [1,2,1].

Example 2:

Input: [0,1,2,2]
Output: 3
Explanation: We can collect [1,2,2].
If we started at the first tree, we would only collect [0, 1].

Example 3:

Input: [1,2,3,2,2]
Output: 4
Explanation: We can collect [2,3,2,2].
If we started at the first tree, we would only collect [1, 2].

Example 4:

Input: [3,3,3,1,2,1,1,2,3,3,4]
Output: 5
Explanation: We can collect [1,2,1,1,2].
If we started at the first tree or the eighth tree, we would only collect 4 fruits.

Note:

1. 1 <= tree.length <= 40000
2. 0 <= tree[i] < tree.length

Pre-requisites

For this question, you will need a good understanding of arrays and pointers. Can you solve this question in your head: