Cracking the Coding Interview, 4 Edition - 150 Programming Interview Questions and Solutions

Solutions to Chapter 9 | Sorting and Searching
9.1 You are given two sorted arrays, A and B, and A has a large enough buffer at the end
to hold B. Write a method to merge B into A in sorted order.
SOLUTION
pg 66
This code is a part of the standard merge-sort code. We merge A and B from the back, by
comparing each element.
1 public static void merge(int[] a, int[] b, int n, int m) {
2 int k = m + n - 1; // Index of last location of array b
3 int i = n - 1; // Index of last element in array b
4 int j = m - 1; // Index of last element in array a
5
6 // Start comparing from the last element and merge a and b
7 while (i >= 0 && j >= 0) {
8 if (a[i] > b[j]) {
9 a[k--] = a[i--];
10 } else {
11 a[k--] = b[j--];
12 }
13 }
14 while (j >= 0) {
15 a[k--] = b[j--];
16 }
17 }
Note: You don’t need to copy the contents of a after running out of b’s. They are
already in place.
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Cracking the Coding Interview | Concepts and Algorithms