归并排序
利用分治的思路,将数组都分开,然后比较大小合并成一个数组
#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 5;
int q[N], tmp[N];int n;
void merge_sort(int q[], int l, int r)
{
if (l >= r)
return;
int mid = l + r >> 1;
merge_sort(q, l, mid);
merge_sort(q, mid + 1, r);
int k = 0;
int i = l;
int j = mid + 1;
while (i <= mid && j <= r)
{
if (q[i] <= q[j])
tmp[k++] = q[i++];
else
tmp[k++] = q[j++];
}
while (i <= mid) tmp[k++] = q[i++];
while (j <= r) tmp[k++] = q[j++];
for (i = l, j = 0; i <= r; i++, j++)
q[i] = tmp[j];
}
int main()
{
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin >> n;
for (int i = 0; i < n; i++)
cin >> q[i];
merge_sort(q, 0, n - 1);
for (int i = 0; i < n; i++)
printf("%d ", q[i]);
return 0;
}
快速排序
它的基本思想是通过一组排序将要排序的数据分割成独立的两部分,其中一部分的所有数据都比另外一部分的所有数据小,然后再按此方法对这两部分数据进行快速排序,整个排序过程可以递归进行,以此使所有数据变成有序序列
#include <bits/stdc++.h>
using namespace std;
int a[10001];
int part(int* r, int low, int hight)
{
int i = low, j = hight, pivot = r[low];
while (i < j)
{
while (i<j && r[j]>pivot)
{
j--;
}
if (i < j)
{
swap(r[i++], r[j]);
}
while (i < j && r[i] <= pivot)
{
i++;
}
if (i < j)
{
swap(r[i], r[j--]);
}
}
return i;
}
void Quicksort(int* r, int low, int hight)
{
int mid;
if (low < hight)
{
mid = part(r, low, hight);
Quicksort(r, low, mid - 1);
Quicksort(r, mid+1, hight);
}
}
int main()
{
int N;
cin >> N;
for (int i = 0; i < N; i++)
{
cin >> a[i];
}
Quicksort(a, 0, N - 1);
for (int i = 0; i < N; i++)
{
cout << a[i] << " ";
}
return 0;
}