LeetCode-Merge Sorted Array

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题目：

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

Note:

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

一般的归并方法：

public void merge(int A[], int m, int B[], int n) {        int C[] = new int[A.length];int i = 0, j = 0, k = 0;while (i < m && j < n) {if (A[i] <= B[j]) {C[k++] = A[i++];} else {C[k++] = B[j++];}}while (i < m) {C[k++] = A[i++];}while (j < n) {C[k++] = B[j++];}System.arraycopy(C, 0, A, 0, m+n);    }

明显这种方法的空间耗费比较大，并且最后还进行了数组的拷贝，也是比较耗时的！换个角度思考，为什么要从头开始比较归并呢？为什么不从数组尾部开始比较归并呢？见如下代码，空间耗费更小，时间更短：

int i = m-1, j = n-1, k = m+n-1;while (i >= 0 && j >= 0) {if (A[i] >= B[j]) {A[k--] = A[i--];} else {A[k--] = B[j--];}}while (i >= 0) {A[k--] = A[i--];}while (j >= 0) {A[k--] = B[j--];}

速度可媲美c++

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