常见的排序算法

//直接插入排序void InsertSort(int *a, size_t n)//将一个数插入到一个有序区间中{assert(a);for (size_t i = 0; i < n - 1; i++){int end = i;int tmp = a[end + 1];for (end; end >= 0; end--){if (a[end] > tmp){a[end + 1] = a[end];}else{break;}}a[end + 1] = tmp;}}//shell排序void ShellSort(int *a, size_t n){int gap = n;while (gap > 1){gap = gap / 3 + 1;//预排序，将整体变得大概有序，最后当gap=1时就是直接插入排序，前面所做的预排序是为直接插入排序做铺垫。for (size_t i = 0; i < n - gap; i++){int end = i;int tmp = a[end + gap];for (end; end >= 0; end--){if (a[end] > tmp){a[end + gap] = a[end];}else{break;}}a[end + gap] = tmp;}}}//选择排序void SelectSort(int* a, size_t n){size_t begin = 0, end = n - 1;while (begin < end){size_t min=begin ,max = begin;for (size_t i = begin; i <= end; i++){if (a[i] < a[min])min = i;if (a[i]>a[max])max = i;}swap(a[begin], a[min]);if (begin == max)//max在头被交换至min处，将min处赋值给max，保证max为最大数的下标{max = min;}swap(a[end], a[max]);begin++;end++;}}//堆排序void Adjustdown(int* a, size_t n, size_t root)//向下调整算法{size_t parent = root;size_t child = parent * 2 + 1;while (child<n){//找大孩if (child + 1 < n&&a[child + 1] > a[child]){child++;}if (a[child] > a[parent]){parent = child;child = parent * 2 + 1;swap(a[child], a[parent]);}else{break;}}}void HeapSort(int* a, size_t n){//建大堆for (size_t i = 0; i < (n - 2) / 2; i--){Adjustdown(a, n, i);}size_t end = n - 1;while (end>0){swap(a[0], a[end]);Adjustdown(a, end, 0);end--;}}//冒泡排序void BubbleSort(int* a, int n){int j = 0;for (int i = 0; i < n - 1 ; i++){int flag = 0;for (j; j < n - i-1; j++){if (a[j]>a[j + 1]){swap(a[j], a[j + 1]);flag = 1;}}if (flag==0){break;}}}//快速排序//左右指针int PartSortLF(int*a, int begin, int end){int key = end;while (begin < end){while (begin < end && a[begin] <= a[key]){++begin;}while (begin < end && a[end] >= a[key]){end--;}if (begin < end){swap(a[begin], a[end]);}}swap(a[begin], a[key]);return begin;}//挖坑int PartSortK(int*a, int begin, int end){int key = a[end];while (begin < end){while (begin < end && a[begin] <= key){++begin;}a[end] = a[begin];while (begin < end && a[end] >= key){end--;}a[begin] = a[end];}a[begin] = key;return begin;}//前后指针int PartSortFB(int*a, int begin, int end){int cur = begin;int prev = cur - 1;while (cur < end){if (a[cur] < a[end] && ++prev != cur)//如果a[cur]<key prev++紧跟cur 如果prev！=cur 就交换；swap(a[cur], a[prev]);cur++;                                 //a[cur]>key,因为是&&前面错不判断后面条件，只有cur++往后走；}swap(a[++prev], a[end]);return prev;}void QuickSort(int* a, int left, int right){                                             //快排可以利用三数取中，和小区间优化进行优化。if (left >= right)                        //三数取中是取一组数头尾中间三数的中位数作为key，return;                               //小区间优化是当区间数的个数小于一定值时，利用直接插入排序，减少递归开销。while (left < right){int div = PartSortLF(a, left, right);QuickSort( a, left, div-1);QuickSort( a, div+1,right);}}//非递归实现快速排序void QuickSortNonR(int* a, int begin, int end)//这里使用栈来模拟递归，如果不知道栈中存什么可以看一看函数的参数{stack<int> s;if (begin < end){s.push(end);                         //s.push(begin);}while (!s.empty()){int begin = s.top();s.pop();int end = s.top();s.pop();int div = PartSortLF(a, begin, end);if (begin < div - 1)//至少还有两个数继续排，这里也可以用小区间优化{s.push(div - 1);s.push(begin);}if (div + 1 < end){s.push(end);s.push(div + 1);}}}//归并排序void Merge(int* a, int* tmp, int begin1, int end1, int begin2, int end2)//将两个空间begin1~end1与begin2~end2归并,这里1区间在2区间左边{int index = begin1;int start = begin1;int finish = end2;while (begin1 <= end1 && begin2 <= end2){if (a[begin1] < a[begin2])tmp[index++] = a[begin1++];else{tmp[index++] = a[begin1++];}}//走到这里1,2两个区间里有一个区间可能没cp完所以要接着cpwhile (begin1 <= end1){tmp[index++] = a[begin1++];}while (begin2 <= end2){tmp[index++] = a[begin2++];}//最后要把tmp中的数据考回a中供上一层递归归并memcpy(a + start, tmp + start, (finish - start + 1)*sizeof(int));//一定要注意这里memcpy是按字节考的一定要乘上sizeoftype否则就会少cp数据}void _MergeSort(int* a, int* tmp, int begin, int end)//将一组数不断地分成小区间，然后将小区间归并起来{if (begin >= end)return;int mid = begin + (end - begin) / 2;//每次分成[begin,mid],[mid+1,end]两个区间_MergeSort(a, tmp, begin, mid);_MergeSort(a, tmp, mid+1,end);//归并区间Merge(a, tmp, begin, mid, mid + 1, end);}