RUST GYM Leetcode 1330 Reverse Subarray To Maximize Array Value Rust Solution

1330. Reverse Subarray To Maximize Array Value

You are given an integer array nums. The value of this array is defined as the sum of |nums[i]-nums[i+1]| for all 0 <= i < nums.length-1.

You are allowed to select any subarray of the given array and reverse it. You can perform this operation only once.

Find maximum possible value of the final array.

Example 1:

Input: nums = [2,3,1,5,4]
Output: 10
Explanation: By reversing the subarray [3,1,5] the array becomes [2,5,1,3,4] whose value is 10.

Example 2:

Input: nums = [2,4,9,24,2,1,10]
Output: 68

Constraints:

1 <= nums.length <= 3*10^4
-10^5 <= nums[i] <= 10^5

Rust Solution

struct Solution;

impl Solution {
    fn max_value_after_reverse(nums: Vec<i32>) -> i32 {
        let n = nums.len();
        let mut res = 0;
        let mut min = std::i32::MAX;
        let mut max = std::i32::MIN;
        let mut total = 0;
        for i in 1..n {
            let a = nums[i - 1];
            let b = nums[i];
            total += (a - b).abs();
            res = res.max((b - nums[0]).abs() - (a - b).abs());
            res = res.max((a - nums[n - 1]).abs() - (a - b).abs());
            min = min.min(a.max(b));
            max = max.max(a.min(b));
        }
        total + res.max((max - min) * 2)
    }
}

#[test]
fn test() {
    let nums = vec![2, 3, 1, 5, 4];
    let res = 10;
    assert_eq!(Solution::max_value_after_reverse(nums), res);
    let nums = vec![2, 4, 9, 24, 2, 1, 10];
    let res = 68;
    assert_eq!(Solution::max_value_after_reverse(nums), res);
}

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