88. Merge Sorted Array

Description

Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.

Note:

• The number of elements initialized in nums1 and nums2 are m and n respectively.

• You may assume that nums1 has enough space (size that is equal to m + n) to hold additional elements from nums2.

Constraints

• -10^9 <= nums1[i], nums2[i] <= 10^9

• nums1.length == m + n

• nums2.length == n

Approach

Links

• GeeksforGeeks

• Leetcode

• ProgramCreek

• YouTube

Examples

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]

Solutions

Solution 1

/**
 * Time complexity : O(m + n)
 * Space complexity : O(1)
 */

class Solution {
    public void merge(int[] nums1, int m, int[] nums2, int n) {
        int k = m+n-1;
        while(m > 0 && n > 0) {
            nums1[k--] = (nums1[m-1] > nums2[n-1])? nums1[--m]: nums2[--n];
        }
        while(n > 0) {
            nums1[k--] = nums2[--n];
        }
    }
}

Solution 2

/**
 * Time complexity : O(m + n)
 * Space complexity : O(1)
 */

class Solution {
    public void merge(int[] nums1, int m, int[] nums2, int n) {
        int k = m+n-1;
        while(k >= 0) {
            if(n < 1 || (m > 0 && nums1[m-1] > nums2[n-1])) {
                nums1[k--] = nums1[--m];
            } else {
                nums1[k--] = nums2[--n];
            }
        }
    }
}

Solution 3

/**
 * Time complexity : O(m * n)
 * Space complexity : O(1)
 */

class Solution {
    public void merge(int[] nums1, int m, int[] nums2, int n) {
        if(m > 0) {
            for(int i = n-1; i >= 0; i--) {
                int j, last = nums1[m-1];

                for(j = m-2; j >= 0 && nums1[j] > nums2[i]; j--) {
                    nums1[j+1] = nums1[j];
                }

                if(j != m-2 || last > nums2[i]) {
                    nums1[j+1] = nums2[i];
                    nums2[i] = last;
                }
            }
        }

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

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