1705. Maximum Number of Eaten Apples

There is a special kind of apple tree that grows apples every day for `n` days. On the `ith` day, the tree grows `apples[i]` apples that will rot after `days[i]` days, that is on day `i + days[i]` the apples will be rotten and cannot be eaten. On some days, the apple tree does not grow any apples, which are denoted by `apples[i] == 0` and `days[i] == 0`.

You decided to eat at most one apple a day (to keep the doctors away). Note that you can keep eating after the first `n` days.

Given two integer arrays `days` and `apples` of length `n`, return the maximum number of apples you can eat.

Example 1:

```Input: apples = [1,2,3,5,2], days = [3,2,1,4,2]
Output: 7
Explanation: You can eat 7 apples:
- On the first day, you eat an apple that grew on the first day.
- On the second day, you eat an apple that grew on the second day.
- On the third day, you eat an apple that grew on the second day. After this day, the apples that grew on the third day rot.
- On the fourth to the seventh days, you eat apples that grew on the fourth day.
```

Example 2:

```Input: apples = [3,0,0,0,0,2], days = [3,0,0,0,0,2]
Output: 5
Explanation: You can eat 5 apples:
- On the first to the third day you eat apples that grew on the first day.
- Do nothing on the fouth and fifth days.
- On the sixth and seventh days you eat apples that grew on the sixth day.
```

Constraints:

• `apples.length == n`
• `days.length == n`
• `1 <= n <= 2 * 104`
• `0 <= apples[i], days[i] <= 2 * 104`
• `days[i] = 0` if and only if `apples[i] = 0`.

1705. Maximum Number of Eaten Apples
``````struct Solution;
use std::cmp::Reverse;
use std::collections::BinaryHeap;

impl Solution {
fn eaten_apples(apples: Vec<i32>, days: Vec<i32>) -> i32 {
let n = apples.len();
let mut queue: BinaryHeap<Reverse<(usize, i32)>> = BinaryHeap::new();
let mut i = 0;
let mut res = 0;
loop {
if i < n {
queue.push(Reverse((i + days[i] as usize, apples[i])));
}
if i >= n && queue.is_empty() {
break;
}
while let Some(Reverse((j, left))) = queue.peek() {
if i >= *j || *left == 0 {
queue.pop();
} else {
break;
}
}
if let Some(mut top) = queue.peek_mut() {
(top.0).1 -= 1;
res += 1;
}
i += 1;
}
res
}
}

#[test]
fn test() {
let apples = vec![1, 2, 3, 5, 2];
let days = vec![3, 2, 1, 4, 2];
let res = 7;
assert_eq!(Solution::eaten_apples(apples, days), res);
let apples = vec![3, 0, 0, 0, 0, 2];
let days = vec![3, 0, 0, 0, 0, 2];
let res = 5;
assert_eq!(Solution::eaten_apples(apples, days), res);
}
``````