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

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Input:
nums1 = [1,2,3,0,0,0], m = 3
nums2 = [2,5,6],       n = 3

Output: [1,2,2,3,5,6]

为什么反过来？

  • 因为nums1后面是空的，说明后面都是0，所以反过来赋值不会覆盖原来的自身的值，否则覆盖。
  • 最后的while，因为如果nums2不是空，就还要赋值；而如果是因为nums1不要紧，因为本身自己的值就在里面
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public void merge(int[] nums1, int m, int[] nums2, int n) {
    int i = m - 1, j = n - 1, k = m + n - 1;
    while (i >= 0 && j >= 0) {
        if (nums1[i] > nums2[j]) nums1[k--] = nums1[i--];
        else nums1[k--] = nums2[j--];
    }
    while (j >= 0) nums1[k--] = nums2[j--];
}