4. 归并排序和快速排序
1.递归形式的归并排序
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#include<iostream> using namespace std; int n; int *a; void merge(int l, int mid, int r, int *b){ int i = l, j = mid + 1, k = 0; while (i <= mid && j <= r) { if (a[i] < a[j]) { b[k] = a[i]; i++; } else { b[k] = a[j]; j++; } k++; } if (i <= mid) { while (i <= mid) { b[k] = a[i]; k++; i++; } } if (j <= r) { while (j <= r) { b[k] = a[j]; k++; j++; } } } void copy(int l, int r, int *b) { int j = 0; for (int i = l; i <= r; i++) a[i] = b[j++]; } void sort(int l, int r) { if (l == r) return; int *b = new int[r - l + 1]; int mid = (l + r) / 2; sort(l, mid); sort(mid + 1, r); merge(l, mid, r, b); copy(l, r, b); delete[] b; } int main() { scanf("%d", &n); a = new int[n]; for (int i = 0; i < n; i++) scanf("%d", &a[i]); sort(0, n - 1); for (int i = 0; i < n; i++) printf("%d ", a[i]); delete[] a; return 0; }
2.非递归形式的归并排序
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#include<iostream> using namespace std; int n; int *a; void merge(int l, int mid, int r, int *b){ if (r > n - 1) r = n - 1; if (mid > n - 1) mid = n - 1; int i = l, j = mid + 1, k = 0; while (i <= mid && j <= r) { if (a[i] < a[j]) { b[k] = a[i]; i++; } else { b[k] = a[j]; j++; } k++; } if (i <= mid) { while (i <= mid) { b[k] = a[i]; k++; i++; } } if (j <= r) { while (j <= r) { b[k] = a[j]; k++; j++; } } } void copy(int l, int r, int *b) { if (r > n - 1) r = n - 1; int j = 0; for (int i = l; i <= r; i++) a[i] = b[j++]; } void sort(){ for (int i = 1; i < n; i += i){ for (int j = 0; j < n; j += 2*i){ int *b = new int[i]; merge(j, j+i-1, j+2*i-1, b); copy(j, j+2*i-1, b); delete[] b; } } } int main() { scanf("%d", &n); a = new int[n]; for (int i = 0; i < n; i++) scanf("%d", &a[i]); sort(); for (int i = 0; i < n; i++) printf("%d ", a[i]); delete[] a; return 0; }
3.快速排序
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#include<iostream> using namespace std; int n; int *a; int partition(int left, int right) { int i = left + 1 ; int j = right; int temp = a[left]; while(i <= j) { while (a[i] < temp) i++; while (a[j] > temp ) j--; if (i < j) swap(a[i++], a[j--]); else i++; } swap(a[j], a[left]); return j; } void quick_sort(int left, int right) { if (left > right) return; int j = partition(left, right); quick_sort(left, j - 1); quick_sort(j + 1, right); } int main() { scanf("%d", &n); a = new int[n]; for (int i = 0; i < n; i++) scanf("%d", &a[i]); quick_sort(0, n - 1); for (int i = 0; i < n; i++) printf("%d ", a[i]); delete[] a; return 0; }
人生不如意的时候,是上帝给的长假,这个时候应该好好享受假期。
突然有一天假期结束,时来运转,人生才是真正开始了。
突然有一天假期结束,时来运转,人生才是真正开始了。