Given an integer array, sort it in ascending order. Use quick sort, merge sort, heap sort or any O(nlogn) algorithm.
分析
Quick Sort
index 0 1 2 3 4 5 6 7 8 9 10 11 12 13
A(key=3)4 1 2 1 5 1 3 2 3 6 2 1 4 3
1 3 1 2 1 5 1 3 2 3 6 2 1 4 4
2 3 1 2 1 1 1 3 2 3 6 2 5 4 4
3 3 1 2 1 1 1 3 2 3 6 2 5 4 4
j i
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 | public class Solution { /** * @param A an integer array * @return void */ public void sortIntegers2(int[] A) { // Write your code here quickSortHelper(A, 0, A.length - 1); } private void quickSortHelper(int[] A, int left, int right) { if(left >= right) return; int i = left, j = right; int key = A[left + (right - left) / 2]; while(i <= j){ while(i <= j && A[i] < key) ++i; while(i <= j && A[j] > key) --j; if(i <= j){ int tmp = A[i]; A[i++] = A[j]; A[j--] = tmp; } } quickSortHelper(A, left, j); quickSortHelper(A, i, right); }} |
Merge Sort
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 | public class Solution { /** * @param A an integer array * @return void */ public void sortIntegers2(int[] A) { // Write your code here int[] tmp = new int[A.length]; mergeSortHelper(A, tmp, 0, A.length - 1); } private void mergeSortHelper(int[] A, int[] tmp, int left, int right) { if(left >= right) return; int mid = left + (right - left) >> 1; mergeSortHelper(A, tmp, left, mid); mergeSortHelper(A, tmp, mid + 1, right); merge(A, tmp, left, mid, right); } private void merge(int[] A, int[] tmp, int left, int mid, int right){ int i = left, j = mid + 1, index = left; while(i <= mid || j <= right){ int a, b, min; a = (i <= mid) ?A[i] : Integer.MAX_VALUE; b = (j <= right) ? A[j] : Integer.MAX_VALUE; min = (a <= b) ?A[i++] : A[j++]; tmp[index++] = min; } for(int k = left; k <= right; k++){ A[k] = tmp[k]; } }} |