2016. Maximum Difference Between Increasing Elements

Given a 0-indexed integer array nums of size n, find the maximum difference between nums[i] and nums[j] (i.e., nums[j] - nums[i]), such that 0 <= i < j < n and nums[i] < nums[j].

Return the maximum difference. If no such i and j exists, return -1.

 

Example 1:

Input: nums = [7,1,5,4]
Output: 4
Explanation:
The maximum difference occurs with i = 1 and j = 2, nums[j] - nums[i] = 5 - 1 = 4.
Note that with i = 1 and j = 0, the difference nums[j] - nums[i] = 7 - 1 = 6, but i > j, so it is not valid.

Example 2:

Input: nums = [9,4,3,2]
Output: -1
Explanation:
There is no i and j such that i < j and nums[i] < nums[j].

Example 3:

Input: nums = [1,5,2,10]
Output: 9
Explanation:
The maximum difference occurs with i = 0 and j = 3, nums[j] - nums[i] = 10 - 1 = 9.

 

Constraints:

  • n == nums.length
  • 2 <= n <= 1000
  • 1 <= nums[i] <= 109

2016. Maximum Difference Between Increasing Elements
struct Solution;

impl Solution {
    fn maximum_difference(nums: Vec<i32>) -> i32 {
        let n = nums.len();
        let mut res = -1;
        for i in 0..n {
            for j in i + 1..n {
                if nums[i] < nums[j] {
                    res = res.max(nums[j] - nums[i]);
                }
            }
        }
        res
    }
}

#[test]
fn test() {
    let nums = vec![7, 1, 5, 4];
    let res = 4;
    assert_eq!(Solution::maximum_difference(nums), res);
    let nums = vec![9, 4, 3, 2];
    let res = -1;
    assert_eq!(Solution::maximum_difference(nums), res);
    let nums = vec![1, 5, 2, 10];
    let res = 9;
    assert_eq!(Solution::maximum_difference(nums), res);
}