_1313.java

package com.fishercoder.solutions;

import java.util.ArrayList;
import java.util.List;

/**
 * 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 [a, b] = [nums[2*i], nums[2*i+1]] (with i >= 0).
 * For each such pair, there are a elements with value b in 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] + [4,4,4,4] is [2,4,4,4].
 *
 * Constraints:
 * 2 <= nums.length <= 100
 * nums.length % 2 == 0
 * 1 <= nums[i] <= 100
 * */
public class _1313 {
    public static class Solution1 {
        public int[] decompressRLElist(int[] nums) {
            List<Integer> list = new ArrayList<>();
            for (int i = 0; i < nums.length - 1; i += 2) {
                int count = nums[i];
                int value = nums[i + 1];
                while (count-- > 0) {
                    list.add(value);
                }
            }
            return list.stream().mapToInt(integer -> integer).toArray();
        }
    }
}