常见排序算法实现
1.快速排序：
1 class QuickSort { 2 public: 3 int* quickSort(int* A, int n) { 4 quickSort(A, 0, n-1); 5 return A; 6 } 7 void quickSort(int* arr, int begin, int end){ 8 if(begin >= end) return; 9 int index = partition(arr, begin, end); 10 quickSort(arr, begin, index-1); 11 quickSort(arr, index+1, end); 12 } 13 int partition(int* arr, int begin, int end){ 14 int pivot=arr[begin]; 15 while(begin < end){ 16 while(begin < end && arr[end] > pivot) 17 --end; 18 if(begin < end) arr[begin] = arr[end]; 19 while(begin < end && arr[begin] <= pivot) 20 ++begin; 21 if(begin < end) arr[end] = arr[begin]; 22 } 23 arr[begin] = pivot; 24 return begin; 25 } 26 };
2. 归并排序
1 class MergeSort { 2 public: 3 int* mergeSort(int* A, int n) { 4 if(n < 2) return A; 5 mergeSort(A, 0, n-1); 6 return A; 7 } 8 void mergeSort(int* A, int l, int r){ 9 if(l == r) return; 10 int mid = (l + r) / 2; 11 mergeSort(A, l, mid); 12 mergeSort(A, mid+1, r); 13 merge(A, l, mid, r); 14 } 15 16 void merge(int* A, int left, int mid, int right){ 17 int* tmp = new int[right-left+1]; 18 int l=left, r=mid+1; 19 int i=0; 20 while(l<=mid && r<=right) 21 tmp[i++] = A[l]<=A[r] ? A[l++] : A[r++]; 22 23 while(l <= mid) 24 tmp[i++] = A[l++]; 25 while(r <= right) 26 tmp[i++] = A[r++]; 27 28 for(int i=0; i<right-left+1; ++i) 29 A[left + i] = tmp[i]; 30 } 31 };
3. 堆排序
https://www.cnblogs.com/chengxiao/p/6129630.html
1 class HeapSort { 2 public: 3 int* heapSort(int* arr, int n) { 4 // 1.构建大顶堆 5 for(int i=n/2-1; i>=0; --i){ 6 adjustHeap(arr, i, n); //从第一个非叶子结点从下至上，从右至左调整结构 7 } 8 //2.调整堆结构+交换堆顶元素与末尾元素 9 for(int i=n-1; i>0; --i){ 10 swap(arr[0], arr[i]); 11 adjustHeap(arr, 0, i); 12 } 13 return arr; 14 } 15 16 void adjustHeap(int* arr, int pos, int len){ 17 int parent=arr[pos]; // 取出当前元素 18 for(int i=2*pos+1; i<len; i=2*i+1){ // 从k结点的左子结点开始，也就是2k+1处开始 19 if(i+1<len && arr[i]<arr[i+1]) // 如果左子结点小于右子结点，i指向右子结点 20 ++i; 21 if(arr[i] > parent){ //如果子节点大于父节点，将子节点值赋给父节点（不用进行交换） 22 arr[pos] = arr[i]; 23 pos = i; 24 }else 25 break; 26 } 27 arr[pos] = parent; 28 } 29 };
4. 希尔排序
1 class ShellSort { 2 public: 3 int* shellSort(int* A, int n) { 4 for(int gap=n/2; gap>=1; gap/=2){ 5 for(int i=gap; i<n; ++i){ 6 int j=i; 7 while(j-gap>=0 && A[j-gap]>A[j]){ 8 swap(A[j-gap], A[j]); 9 j-=gap; 10 } 11 } 12 } 13 return A; 14 } 15 };
5. 计数排序
1 class CountingSort { 2 public: 3 int* countingSort(int* A, int n) { 4 int max_v = *max_element(A, A+n); 5 int min_v = *min_element(A, A+n); 6 int size = max_v - min_v + 1; 7 int* count = new int[size](); // 有括号才有初始值0 8 for(int i=0; i<n; ++i){ 9 ++count[A[i] - min_v]; 10 } 11 12 int j=0; 13 for(int i=0; i<size; ++i){ 14 while(count[i]--) 15 A[j++] = min_v + i; 16 } 17 return A; 18 } 19 };
