/* * 排序算法 */class Solution { public void swap(int[] arr, int i, int j) { int temp = arr[j]; arr[j] = arr[i]; arr[i] = temp; } // 间接插入排序, O(n^2), 稳固 public void directInsert(int[] arr) { for (int i = 0; i < arr.length; i ++) { for (int j = 0; j < i; j ++) { if (arr[j] > arr[i]) { int temp = arr[i]; System.arraycopy(arr, j, arr, j + 1, i - j); arr[j] = temp; } } } } // 折半插入排序，O(nlogn)，稳固 public void binaryInsert(int[] arr) { for (int i = 0; i < arr.length; i ++) { int left = 0, right = i - 1; while (left <= right) { int mid = left + (right - left) / 2; if (arr[mid] < arr[i]) { left = mid + 1; } else { right = mid - 1; } } int temp = arr[i]; System.arraycopy(arr, left, arr, left + 1, i - left); arr[left] = temp; } } // 抉择排序， O(n^2)，不稳固 public void directSelect(int[] arr) { for (int i = 0; i < arr.length - 1; i ++) { for (int j = i + 1; j < arr.length; j ++) { if (arr[i] > arr[j]) { swap(arr, i, j); } } } } // 堆排序， O(nlogn)，不稳固，最大堆 public void heap(int[] arr) { for (int i = arr.length - 1; i >= 0; i --) { for (int j = i / 2 - 1; j >= 0; j --) { if (j * 2 + 1 == i && i % 2 == 1) { if (arr[j] < arr[j * 2 + 1]) { swap(arr, j, j * 2 + 1); } } else { if (arr[j] < arr[j * 2 + 1]) { swap(arr, j, j * 2 + 1); } if (arr[j] < arr[j * 2 + 2]) { swap(arr, j, j * 2 + 2); } } } swap(arr, 0, i); } } // 冒泡排序，O(n^2), 稳固 public void bubble(int[] arr) { for (int i = arr.length - 1; i >= 0; i --) { for (int j = 0; j < i; j ++) { if (arr[j] > arr[j + 1]) { swap(arr, j, j + 1); } } } } // 快排，O(nlogn)，不稳固 public void quick(int[] arr) { quickSort(arr, 0, arr.length - 1); } private void quickSort(int[] arr, int left, int right) { if (arr == null || left >= right || arr.length <= 1) { return; } int mid = partition(arr, left, right); quickSort(arr, left, mid); quickSort(arr, mid + 1, right); } private int partition(int[] arr, int left, int right) { int temp = arr[left]; while (left < right) { while (left < right && temp <= arr[right]) { right --; } if (left < right) { arr[left] = arr[right]; left ++; } while (left < right && temp >= arr[left]) { left ++; } if (left < right) { arr[right] = arr[left]; right --; } } arr[left] = temp; return left; } // 归并排序， O(nlogn)， 稳固 public void mergeSort(int[] arr) { sort(arr, 0, arr.length - 1); } private void sort(int[] arr, int left, int right) { if (left < right) { int mid = left + (right - left) / 2; sort(arr, left, mid); sort(arr, mid + 1, right); merge(arr, left, mid, right); } } private void merge(int[] arr, int left, int mid, int right) { int[] temp = new int[right - left + 1]; int i = left, j = mid + 1, index = 0; while (i <= mid && j <= right) { if (arr[i] <= arr[j]) { temp[index ++] = arr[i ++]; } else { temp[index ++] = arr[j ++]; } } while (i <= mid) { temp[index ++] = arr[i ++]; } while (j <= right) { temp[index ++] = arr[j ++]; } for (int k = 0; k < temp.length; k ++) { arr[left ++] = temp[k]; } }}