1313. Decompress Run-Length Encoded List

We are given a list nums of integers representing a list compressed with run-length encoding.

Consider each adjacent pair of elements [freq, val] = [nums[2*i], nums[2*i+1]] (with i >= 0).  For each such pair, there are freq elements with value val concatenated in a sublist. Concatenate all the sublists from left to right to generate the decompressed list.

Return the decompressed list.

 

Example 1:

Input: nums = [1,2,3,4]
Output: [2,4,4,4]
Explanation: The first pair [1,2] means we have freq = 1 and val = 2 so we generate the array [2].
The second pair [3,4] means we have freq = 3 and val = 4 so we generate [4,4,4].
At the end the concatenation [2] + [4,4,4] is [2,4,4,4].

Example 2:

Input: nums = [1,1,2,3]
Output: [1,3,3]

 

Constraints:

  • 2 <= nums.length <= 100
  • nums.length % 2 == 0
  • 1 <= nums[i] <= 100

Rust Solution

struct Solution;

impl Solution {
    fn decompress_rl_elist(nums: Vec<i32>) -> Vec<i32> {
        let mut res = vec![];
        for p in nums.chunks(2) {
            let a = p[0] as usize;
            let b = p[1];
            for _ in 0..a {
                res.push(b);
            }
        }
        res
    }
}

#[test]
fn test() {
    let nums = vec![1, 2, 3, 4];
    let res = vec![2, 4, 4, 4];
    assert_eq!(Solution::decompress_rl_elist(nums), res);
}

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