常用排序算法模板

Posted 2021-05-29 onlyblues

　　这里就不再介绍算法的实现原理，直接给出常用的排序算法模板，包括冒泡排序，插入排序，希尔排序，选择排序，堆排序，归并排序，快速排序。这些代码都是我个人常用的模板，代码也比较的简短精炼。若解题有需要，直接套模板即可。

 

冒泡排序(Bubble Sort)

 1 void bubbleSort(int *a, int n) {
 2     for (int i = 0; i < n - 1; i++) {
 3         bool flag = false;
 4         for (int j = 0; j < n - 1 - i; j++) {
 5             if (a[j] > a[j + 1]) {
 6                 std::swap(a[j], a[j + 1]);
 7                 flag = true;
 8             }
 9         }
10         if (flag == false) break;
11     }
12 }

 

插入排序(Insertion Sort)

1 void insertionSort(int *a, int n) {
2     for (int i = 1; i < n; i++) {
3         int tmp = a[i], j = i;
4         for ( ; j > 0 && tmp < a[j - 1]; j--) {
5             a[j] = a[j - 1];
6         }
7         a[j] = tmp;
8     }
9 }

 

希尔排序(Shell Sort)

 1 void shellSort(int *a, int n) {
 2     for (int k = n >> 1; k; k >>= 1) {
 3         for (int i = k; i < n; i++) {
 4             int tmp = a[i], j = i;
 5             for ( ; j >= k && tmp < a[j - k]; j -= k) {
 6                 a[j] = a[j - k];
 7             }
 8             a[j] = tmp;
 9         }
10     }
11 }

 

选择排序(Selection Sort)

1 void selectSort(int *a, int n) {
2     for (int i = 0; i < n; i++) {
3         int minId = i;
4         for (int j = i + 1; j < n; j++) {
5             if (a[j] < a[minId]) minId = j;
6         }
7         std::swap(a[i], a[minId]);
8     }
9 }

 

堆排序(Heap Sort)

 1 void percDown(int *a, int n, int pos) {
 2     int tmp = a[pos], parent = pos;
 3     for (int child = parent * 2 + 1; child < n; parent = child, child = parent * 2 + 1) {
 4         if (child != n - 1 && a[child + 1] > a[child]) child++;
 5         if (tmp >= a[child]) break;
 6         else a[parent] = a[child];
 7     }
 8     a[parent] = tmp;
 9 }
10 
11 void heapSort(int *a, int n) {
12     for (int i = n / 2; i >= 0; i--) {
13         percDown(a, n, i);
14     }
15     for (int i = n - 1; i > 0; i--) {
16         std::swap(a[0], a[i]);
17         percDown(a, i, 0);
18     }
19 }

 

归并排序(Merge Sort)

　　递归版本：

 1 void mergeSort(int *a, int low, int high) {
 2     if (low >= high) return;
 3     int mid = low + high >> 1;
 4     mergeSort(a, low, mid);
 5     mergeSort(a, mid + 1, high);
 6     
 7     int i = low, j = mid + 1, k = 0;
 8     int tmp[high - low + 1];
 9     while (i <= mid && j <= high) {
10         if (a[i] <= a[j]) tmp[k++] = a[i++];
11         else tmp[k++] = a[j++];
12     }
13     while (i <= mid) {
14         tmp[k++] = a[i++];
15     }
16     while (j <= high) {
17         tmp[k++] = a[j++];
18     }
19     for (int i = 0; i < k; i++) {
20         a[low + i] = tmp[i];
21     } 
22 }

　　用STL中的std::merge，来减少代码量：

 1 void mergeSort(int *a, int low, int high) {
 2     if (low >= high) return;
 3     int mid = low + high >> 1;
 4     mergeSort(a, low, mid);
 5     mergeSort(a, mid + 1, high);
 6     
 7     int tmp[high - low + 1];
 8     std::merge(a + low, a + mid + 1, a + mid + 1, a + high + 1, tmp);
 9     std::copy(tmp, tmp + high - low + 1, a + low);
10 }

　　非递归版本：

 1 void mergeSort(int *a, int n) {
 2     int tmp[n];
 3     for (int len = 1; len < n; len <<= 1) {
 4         int mid, right;
 5         for (int left = 0; left < n - len; left = right) {
 6             mid = left + len, right = std::min(mid + len, n);
 7             std::merge(a + left, a + mid, a + mid, a + right, tmp + left);
 8         }
 9         std::copy(tmp, tmp + right, a);
10     }
11 }

 

快速排序(Quick Sort)

 1 void qSort(int *a, int low, int high) {
 2     if (low >= high) return;
 3     int pivot = a[low + high >> 1];
 4     int i = low - 1, j = high + 1;
 5     while (i < j) {
 6         while (a[++i] < pivot);
 7         while (a[--j] > pivot);
 8         if (i < j) std::swap(a[i], a[j]);
 9     }
10     qSort(a, low, j);
11     qSort(a, j + 1, high);
12 }