课外题:需要排序的子数组

#include <iostream>
#define max_length 20
using namespace std;

int length;
int a[max_length] = {2, 3, 7, 5, 4, 6};
int result[4];

void incre_sort(int a[])
{
    int p = -1, q = -1; //左右扫描
    int max = a[0], min = a[length - 1];
    for (int i = 0; i < length; i++)
    {
        //左端拐点其实没必要找到，只要找到最高点，在最高点右边的都要纳入排序范围
        // if (i < length - 1 && a[i] > a[i + 1] && p == -1) //出现第一个拐点用p记录下来
        // {
        //     p = i;
        // }
        if (a[i] > max)
            max = a[i];
        if (a[i] < max)
            q = i;
    }
    //拓展左端点，从最右端开始，比最小点大的都要纳入排序范围,因为最小点一定要排到最左边  2,3,7,4,1,5,6
    for (int i = length - 1; i >= 0; i--)
    {
        if (a[i] < min)
            min = a[i];
        if (a[i] > min)
            p = i;
    }
    result[0] = p;
    result[1] = q;
}

void decre_sort(int a[]) //对incre_sort略微改动即可
{
    int p = -1, q = -1; //左右扫描
    int max = a[length - 1], min = a[0];
    for (int i = 0; i < length; i++)
    {
        if (a[i] < min)
            min = a[i];
        if (a[i] > min)
            q = i;
    }
    for (int i = length - 1; i >= 0; i--)
    {
        if (a[i] > max)
            max = a[i];
        if (a[i] < max)
            p = i;
    }
    result[2] = p;
    result[3] = q;
}

int main()
{
    length = 6;
    // cin>>length;
    incre_sort(a);
    decre_sort(a);
    if (result[1] - result[0] < result[3] - result[2])//升序降序比较，得到最短需要排序的子数组
        cout << result[0] << ' ' << result[1] << endl;
    else
    {
        cout << result[2] << ' ' << result[3] << endl;
    }

    return 0;
}