88.Merge Sorted Array

1.Description(Easy)

Given two sorted integer arrays A and B, merge B into A as one sorted array.

Notice

You may assume that A has enough space (size that is greater or equal tom+n) to hold additional elements from B. The number of elements initialized in A and B are m and n respectively.

Example

A =[1, 2, 3, empty, empty], B =[4, 5]

After merge, A will be filled as[1, 2, 3, 4, 5]

2.Code

1. Merge two sorted array是正向扫描，这个题目是反向扫描。

因为在A数组里预留了空间

public void mergeSortedArray(int[] A, int m, int[] B, int n) {
        int indexA=m-1;
        int indexB=n-1;
        int index=m+n-1;
        while(indexA>=0 && indexB>=0){
            if(A[indexA]>B[indexB]){
                A[index]=A[indexA];
                indexA--;
            }else{
                A[index]=B[indexB];
                indexB--;
            }
            index--;
        }
        while(indexA>=0){
            A[index--]=A[indexA--];
        }
        while(indexB>=0){
            A[index--]=B[indexB--];
        }
    }

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