lc-88

//You are given two integer arrays nums1 and nums2, sorted in non-decreasing ord
//er, and two integers m and n, representing the number of elements in nums1 and n
//ums2 respectively. 
//
// Merge nums1 and nums2 into a single array sorted in non-decreasing order. 
//
// The final sorted array should not be returned by the function, but instead be
// stored inside the array nums1. To accommodate this, nums1 has a length of m + n
//, where the first m elements denote the elements that should be merged, and the 
//last n elements are set to 0 and should be ignored. nums2 has a length of n. 
//
// 
// Example 1: 
//
// 
//Input: nums1 = [1,2,3,0,0,0], m = 3, nums2 = [2,5,6], n = 3
//Output: [1,2,2,3,5,6]
//Explanation: The arrays we are merging are [1,2,3] and [2,5,6].
//The result of the merge is [1,2,2,3,5,6] with the underlined elements coming f
//rom nums1.
// 
//
// Example 2: 
//
// 
//Input: nums1 = [1], m = 1, nums2 = [], n = 0
//Output: [1]
//Explanation: The arrays we are merging are [1] and [].
//The result of the merge is [1].
// 
//
// Example 3: 
//
// 
//Input: nums1 = [0], m = 0, nums2 = [1], n = 1
//Output: [1]
//Explanation: The arrays we are merging are [] and [1].
//The result of the merge is [1].
//Note that because m = 0, there are no elements in nums1. The 0 is only there t
//o ensure the merge result can fit in nums1.
// 
//
// 
// Constraints: 
//
// 
// nums1.length == m + n 
// nums2.length == n 
// 0 <= m, n <= 200 
// 1 <= m + n <= 200 
// -109 <= nums1[i], nums2[j] <= 109 
// 
//
// 
// Follow up: Can you come up with an algorithm that runs in O(m + n) time? 
// Related Topics Array Two Pointers Sorting 
// 👍 6787 👎 599


//leetcode submit region begin(Prohibit modification and deletion)
class Solution {
    public void merge(int[] nums1, int m, int[] nums2, int n) {
        if (n == 0) {
            return;
        }

        if (m == 0) {
            for (int i = 0; i < n; i++) {
                nums1[i] = nums2[i];
            }

            return;
        }

        int index1 = m + n - 1, index2 = m - 1;
        while(index2 >= 0) {
            nums1[index1--] = nums1[index2--];
        }

        index1++;
        index2 = 0;
        int index = 0;

        while (index < m + n) {
            if (index1 == m + n) {
                nums1[index++] = nums2[index2++];
                continue;
            }

            if (index2 == n) {
                nums1[index++] = nums1[index1++];
                continue;
            }

            if (nums1[index1] < nums2[index2]) {
                nums1[index++] = nums1[index1++];
            } else {
                nums1[index++] = nums2[index2++];
            }
        }

    }
}
//leetcode submit region end(Prohibit modification and deletion)