排序

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几个排序方式的模板

冒泡排序

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#include <iostream>

using namespace std;

int a[100],n;

int main()
{
    cin >> n;
    for (int i = 1; i <= n; i++)
        scanf("%d", &a[i]);
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= n - i; j++)
            if (a[j] > a[j + 1])
                swap(a[j], a[j + 1]);
    for (int i = 1; i <= n; i++)
        printf("%d ", a[i]);
    return 0;
}

快速排序

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#include <iostream>
#include <cstdio>

using namespace std;

const int MAXN = 1e6 + 10;

int a[MAXN];
int n;

void quicksort(int l, int r)
{
    if (l == r)
        return;
    int x = a[(l + r + 1) / 2], i = l - 1, j = r + 1; //int x=a[(l+r)/2]
    while (i < j)
    {
        while (a[++i] < x);
        while (a[--j] > x);
        if (i < j)
            swap(a[i], a[j]);
    }
    quicksort(l, i - 1); //quicksort(l,j);
    quicksort(i, r);     //quicksort(j+1,r);
}

int main()
{
    scanf("%d", &n);
    for (int i = 1; i <= n; i++)
        scanf("%d", &a[i]);
    quicksort(1, n);
    for (int i = 1; i <= n; i++)
        printf("%d ", a[i]);
    return 0;
}

归并排序

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#include <iostream>

using namespace std;

const int N = 1e6 + 10;

int a[N], tem[N], n;

void mergesort(int a[], int l, int r)
{
    if (l >= r)
        return;
    int mid = (l + r) / 2;
    mergesort(a, l, mid), mergesort(a, mid + 1, r);
    int k = 0, i = l, j = mid + 1;
    while (i <= mid && j <= r)
    {
        if (a[i] < a[j])
            tem[k++] = a[i++];
        else
            tem[k++] = a[j++];
    }
    while (i <= mid)
        tem[k++] = a[i++];
    while (j <= r)
        tem[k++] = a[j++];
    for (int i = 0; i < k; i++)
        a[l + i] = tem[i];
}

int main()
{
    scanf("%d", &n);
    for (int i = 1; i <= n; i++)
        scanf("%d", &a[i]);
    mergesort(a, 1, n);
    for (int i = 1; i <= n; i++)
        printf("%d ", a[i]);
    return 0;
}