public static int[] merge(int[] a, int[] b) { int[] answer = new int[a.length + b.length]; int i = 0, j = 0, k = 0; while (i < a.length && j < b.length) answer[k++] = a[i] < b[j] ? a[i++] : b[j++]; while (i < a.length) answer[k++] = a[i++]; while (j < b.length) answer[k++] = … Read more
Knuth left this as an exercise (Vol 3, 5.2.5). There do exist in-place merge sorts. They must be implemented carefully. First, naive in-place merge such as described here isn’t the right solution. It downgrades the performance to O(N2). The idea is to sort part of the array while using the rest as working area for … Read more
Quicksort has O(n2) worst-case runtime and O(nlogn) average case runtime. However, it’s superior to merge sort in many scenarios because many factors influence an algorithm’s runtime, and, when taking them all together, quicksort wins out. In particular, the often-quoted runtime of sorting algorithms refers to the number of comparisons or the number of swaps necessary … Read more