88. Merge Sorted Array
Tags: ‘Array’, ‘Two Pointers’
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 greater or equal to m + n) to hold additional elements from nums2.
Example:
Input: nums1 = [1,2,3,0,0,0], m = 3 nums2 = [2,5,6], n = 3 Output: [1,2,2,3,5,6]
Solution
方法1： 从后往前merge，可以避免用额外空间 做到O(1)
public void merge(int[] nums1, int m, int[] nums2, int n) {
int i = m - 1, j = n - 1, p = m + n - 1;
while (i >= 0 && j >= 0) {
if (nums1[i] > nums2[j]) {
nums1[p--] = nums1[i--];
} else {
nums1[p--] = nums2[j--];
}
}
while (j >= 0) {
nums1[p--] = nums2[j--];
}
}