## 1176. Diet Plan Performance

A dieter consumes `calories[i]` calories on the `i`-th day.

Given an integer `k`, for every consecutive sequence of `k` days (`calories[i], calories[i+1], ..., calories[i+k-1]` for all `0 <= i <= n-k`), they look at T, the total calories consumed during that sequence of `k` days (`calories[i] + calories[i+1] + ... + calories[i+k-1]`):

• If `T < lower`, they performed poorly on their diet and lose 1 point;
• If `T > upper`, they performed well on their diet and gain 1 point;
• Otherwise, they performed normally and there is no change in points.

Initially, the dieter has zero points. Return the total number of points the dieter has after dieting for `calories.length` days.

Note that the total points can be negative.

Example 1:

```Input: calories = [1,2,3,4,5], k = 1, lower = 3, upper = 3
Output: 0
Explanation: Since k = 1, we consider each element of the array separately and compare it to lower and upper.
calories and calories are less than lower so 2 points are lost.
calories and calories are greater than upper so 2 points are gained.
```

Example 2:

```Input: calories = [3,2], k = 2, lower = 0, upper = 1
Output: 1
Explanation: Since k = 2, we consider subarrays of length 2.
calories + calories > upper so 1 point is gained.
```

Example 3:

```Input: calories = [6,5,0,0], k = 2, lower = 1, upper = 5
Output: 0
Explanation:
calories + calories > upper so 1 point is gained.
lower <= calories + calories <= upper so no change in points.
calories + calories < lower so 1 point is lost.
```

Constraints:

• `1 <= k <= calories.length <= 10^5`
• `0 <= calories[i] <= 20000`
• `0 <= lower <= upper`

## Rust Solution

``````struct Solution;

impl Solution {
fn update(sum: i32, lower: i32, upper: i32, point: &mut i32) {
if sum < lower {
*point -= 1;
}
if sum > upper {
*point += 1;
}
}
fn diet_plan_performance(calories: Vec<i32>, k: i32, lower: i32, upper: i32) -> i32 {
let mut sum = 0;
let mut point = 0;
let n = calories.len();
let k = k as usize;
for i in 0..k {
sum += calories[i];
}
Self::update(sum, lower, upper, &mut point);
for i in 0..n - k {
sum -= calories[i];
sum += calories[i + k];
Self::update(sum, lower, upper, &mut point);
}
point
}
}

#[test]
fn test() {
let calories: Vec<i32> = vec![1, 2, 3, 4, 5];
let k = 1;
let lower = 3;
let upper = 3;
let res = 0;
assert_eq!(
Solution::diet_plan_performance(calories, k, lower, upper),
res
);
let calories: Vec<i32> = vec![3, 2];
let k = 2;
let lower = 0;
let upper = 1;
let res = 1;
assert_eq!(
Solution::diet_plan_performance(calories, k, lower, upper),
res
);
let calories: Vec<i32> = vec![6, 5, 0, 0];
let k = 2;
let lower = 1;
let upper = 5;
let res = 0;
assert_eq!(
Solution::diet_plan_performance(calories, k, lower, upper),
res
);
}
``````

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