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📜  检查旋转后是否可以对数组排序

📅  最后修改于: 2021-06-25 18:46:07             🧑  作者: Mango

给定大小为N的数组,任务是确定是否可以仅通过一次随机排序对数组进行排序。一次混洗中,我们可以将一些连续的元素从数组的末端移开,并将其放置在数组的前面。
例如:

例子:

Input: arr[] = {1, 2, 3, 4} 
Output: Possible 
Since this array is already sorted hence no need for shuffle.

Input: arr[] = {6, 8, 1, 2, 5}
Output: Possible
Place last three elements at the front 
in the same order i.e. {1, 2, 5, 6, 8}

方法:

  1. 检查数组是否已排序。如果是,则返回true。
  2. 否则,开始遍历数组元素,直到当前元素小于下一个元素。将索引存储在arr [i]> arr [i + 1]。
  3. 从该点开始遍历,并检查该索引元素是否按升序排列。
  4. 如果同时满足以上两个条件,则检查最后一个元素是否小于或等于给定数组的第一个元素。
  5. 如果满足以上三个条件,则打印“可能”,否则,如果以上三个条件中的任何一个失败,则打印“不可能”。

下面是上述方法的实现:

C++
// C++ implementation of above approach
#include 
using namespace std;
 
// Function to check if it is possible
bool isPossible(int a[], int n)
{
    // step 1
    if (is_sorted(a, a + n)) {
        cout << "Possible" << endl;
    }
 
    else {
 
        // break where a[i] > a[i+1]
        bool flag = true;
        int i;
        for (i = 0; i < n - 1; i++) {
            if (a[i] > a[i + 1]) {
                break;
            }
        }
        // break point + 1
        i++;
 
        // check whether the sequence is
        // further increasing or not
        for (int k = i; k < n - 1; k++) {
            if (a[k] > a[k + 1]) {
                flag = false;
                break;
            }
        }
 
        // If not increasing after break point
        if (!flag)
            return false;
 
        else {
 
            // last element <= First element
            if (a[n - 1] <= a[0])
                return true;
 
            else
                return false;
        }
    }
}
 
// Driver code
int main()
{
 
    int arr[] = { 3, 1, 2, 2, 3 };
    int n = sizeof(arr) / sizeof(arr[0]);
 
    if (isPossible(arr, n))
        cout << "Possible";
 
    else
        cout << "Not Possible";
 
    return 0;
}


Java
// Java implementation of above approach
class solution
{
    //check if array is sorted
static boolean is_sorted(int a[],int n)
{
    int c1=0,c2=0;
    //if array is ascending
    for(int i=0;i a[i+1]
        boolean flag = true;
        int i;
        for (i = 0; i < n - 1; i++) {
            if (a[i] > a[i + 1]) {
                break;
            }
        }
        // break point + 1
        i++;
   
        // check whether the sequence is
        // further increasing or not
        for (int k = i; k < n - 1; k++) {
            if (a[k] > a[k + 1]) {
                flag = false;
                break;
            }
        }
   
        // If not increasing after break point
        if (!flag)
            return false;
   
        else {
   
            // last element <= First element
            if (a[n - 1] <= a[0])
                return true;
   
            else
                return false;
        }
    }
    return false;
}
   
// Driver code
public static void main(String[] args)
{
   
    int arr[] = { 3, 1, 2, 2, 3 };
    int n = arr.length;
   
    if (isPossible(arr, n))
        System.out.println("Possible");
   
    else
        System.out.println("Not Possible");
   
}
}
//contributed by Arnab Kundu


Python 3
# Python 3 implementation of
# above approach
def is_sorted(a):
    all(a[i] <= a[i + 1]
    for i in range(len(a) - 1))
     
# Function to check if
# it is possible
def isPossible(a, n):
 
    # step 1
    if (is_sorted(a)) :
        print("Possible")
     
    else :
 
        # break where a[i] > a[i+1]
        flag = True
        for i in range(n - 1) :
            if (a[i] > a[i + 1]) :
                break
             
        # break point + 1
        i += 1
 
        # check whether the sequence is
        # further increasing or not
        for k in range(i, n - 1) :
            if (a[k] > a[k + 1]) :
                flag = False
                break
 
        # If not increasing after
        # break point
        if (not flag):
            return False
 
        else :
 
            # last element <= First element
            if (a[n - 1] <= a[0]):
                return True
 
            else:
                return False
 
# Driver code
if __name__ == "__main__":
 
    arr = [ 3, 1, 2, 2, 3 ]
    n = len(arr)
 
    if (isPossible(arr, n)):
        print("Possible")
 
    else:
        print("Not Possible")
 
# This code is contributed
# by ChitraNayal


C#
// C# implementation of above approach
using System;
class GFG
{
// check if array is sorted
static bool is_sorted(int []a, int n)
{
    int c1 = 0, c2 = 0;
     
    // if array is ascending
    for(int i = 0; i < n - 1; i++)
    {
        if(a[i] <= a[i + 1])
        c1++;
    }
     
    // if array is descending
    for(int i = 1; i < n; i++)
    {
        if(a[i] <= a[i - 1])
        c2++;
    }
    if(c1 == n || c2 == n)
    return true;
     
    return false;
}
 
// Function to check if it is possible
static bool isPossible(int []a, int n)
{
    // step 1
    if (is_sorted(a,n))
    {
        Console.WriteLine("Possible");
    }
 
    else
    {
 
        // break where a[i] > a[i+1]
        bool flag = true;
        int i;
        for (i = 0; i < n - 1; i++)
        {
            if (a[i] > a[i + 1])
            {
                break;
            }
        }
         
        // break point + 1
        i++;
 
        // check whether the sequence is
        // further increasing or not
        for (int k = i; k < n - 1; k++)
        {
            if (a[k] > a[k + 1])
            {
                flag = false;
                break;
            }
        }
 
        // If not increasing after
        // break point
        if (!flag)
            return false;
 
        else
        {
 
            // last element <= First element
            if (a[n - 1] <= a[0])
                return true;
 
            else
                return false;
        }
    }
    return false;
}
 
// Driver code
public static void Main()
{
 
    int []arr = { 3, 1, 2, 2, 3 };
    int n = arr.Length;
 
    if (isPossible(arr, n))
        Console.WriteLine("Possible");
 
    else
        Console.WriteLine("Not Possible");
}
}
 
// This code is contributed by anuj_67


PHP
 a[i+1]
        $flag = true;
        $i;
        for ($i = 0; $i < $n - 1; $i++)
        {
            if ($a[$i] > $a[$i + 1])
            {
                break;
            }
        }
         
        // break point + 1
        $i++;
 
        // check whether the sequence is
        // further increasing or not
        for ($k = $i; $k < $n - 1; $k++)
        {
            if ($a[$k] > $a[$k + 1])
            {
                $flag = false;
                break;
            }
        }
 
        // If not increasing after
        // break point
        if (!$flag)
            return false;
 
        else
        {
 
            // last element <= First element
            if ($a[$n - 1] <= $a[0])
                return true;
 
            else
                return false;
        }
    }
}
 
// Driver code
$arr = array( 3, 1, 2, 2, 3 );
$n = sizeof($arr);
 
if (isPossible($arr, $n))
    echo "Possible";
else
    echo "Not Possible";
 
// This code is contributed
// by Akanksha Rai(Abby_akku)
?>


Javascript


输出:
Possible

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