检查给定数组是否以螺旋方式排序

给定一个大小为N的数组arr[] ，任务是检查数组是否是螺旋排序的。如果发现是真的，则打印“YES” 。否则，打印“NO” 。

注意：如果arr[0] ≤ arr[N – 1] ≤ arr[1] ≤ arr[N – 2] …

例子：

Input: arr[] = { 1, 10, 14, 20, 18, 12, 5 } 
Output: YES 
Explanation: 
arr[0] < arr[6]
arr[1] < arr[5]
arr[2] < arr[4]
Therefore, the required output is YES.

Input: arr[] = { 1, 2, 4, 3 } 
Output: NO

方法：这个想法是遍历数组，对于每个数组元素，比如arr[i] ，检查arr[i]是否小于或等于arr[N – i – 1]和arr[N – i – 1]小于或等于arr[i + 1]或不。如果发现是假的，则打印“NO” 。否则，如果所有数组元素都满足条件，则打印“YES” 。请按照以下步骤解决问题：

• 初始化两个变量，比如start和end ，以存储给定数组的开始和结束索引。
• 在start小于end时迭代一个循环，并检查arr[start] 是否小于或等于arr[end]并且arr[end]是否小于或等于arr[start + 1] 。如果发现是假的，则打印“NO” 。
• 否则，打印“YES” 。

下面是上述方法的实现：

C++14

// C++ program to implement
// the above approach
#include 
using namespace std;
 
// Function to check if the array is
// spirally sorted or not
bool isSpiralSorted(int arr[], int n)
{
 
    // Stores start index
    // of the array
    int start = 0;
 
    // Stores end index
    // of an array
    int end = n - 1;
 
    while (start < end) {
 
        // If arr[start]
        // greater than arr[end]
        if (arr[start] > arr[end]) {
            return false;
        }
 
        // Update start
        start++;
 
        // If arr[end]
        // greater than arr[start]
        if (arr[end] > arr[start]) {
            return false;
        }
 
        // Update end
        end--;
    }
 
    return true;
}
 
// Driver Code
int main()
{
    int arr[] = { 1, 10, 14, 20, 18, 12, 5 };
 
    int N = sizeof(arr) / sizeof(arr[0]);
 
    // Function Call
    if (isSpiralSorted(arr, N))
        cout << "YES" << endl;
    else
        cout << "NO" << endl;
    return 0;
}

Java

// Java program to implement
// the above approach
import java.util.*;
 
class GFG{
 
  // Function to check if the array is
  // spirally sorted or not
  static boolean isSpiralSorted(int[] arr, int n)
  {
 
    // Stores start index
    // of the array
    int start = 0;
 
    // Stores end index
    // of an array
    int end = n - 1;
 
    while (start < end)
    {
 
      // If arr[start]
      // greater than arr[end]
      if (arr[start] > arr[end])
      {
        return false;
      }
 
      // Update start
      start++;
 
      // If arr[end]
      // greater than arr[start]
      if (arr[end] > arr[start])
      {
        return false;
      }
 
      // Update end
      end--;
    }       
    return true;
  }
 
  // Driver code
  public static void main(String[] args)
  {
    int[] arr = { 1, 10, 14, 20, 18, 12, 5 };  
    int N = arr.length;
 
    // Function Call
    if (isSpiralSorted(arr, N) != false)
      System.out.print("YES");
    else
      System.out.print("NO");
  }
}
 
// This code is contributed by sanjoy_62

Python3

# Python3 program to implement
# the above approach
 
# Function to check if the array is
# spirally sorted or not
def isSpiralSorted(arr, n) :
 
    # Stores start index
    # of the array
    start = 0;
 
    # Stores end index
    # of an array
    end = n - 1;
    while (start < end) :
 
        # If arr[start]
        # greater than arr[end]
        if (arr[start] > arr[end]) :
            return False;
 
        # Update start
        start += 1;
 
        # If arr[end]
        # greater than arr[start]
        if (arr[end] > arr[start]) :
            return False;
 
        # Update end
        end -= 1;
    return True;
 
# Driver Code
if __name__ ==  "__main__" :
    arr = [ 1, 10, 14, 20, 18, 12, 5 ];
    N = len(arr);
 
    # Function Call
    if (isSpiralSorted(arr, N)) :
        print("YES");
    else :
        print("NO");
         
    # This code is contributed by AnkThon

C#

// C# program to implement
// the above approach
using System;
using System.Collections.Generic;
class GFG
{
     
    // Function to check if the array is
    // spirally sorted or not
    static bool isSpiralSorted(int[] arr, int n)
    {
       
        // Stores start index
        // of the array
        int start = 0;
       
        // Stores end index
        // of an array
        int end = n - 1;
       
        while (start < end)
        {
       
            // If arr[start]
            // greater than arr[end]
            if (arr[start] > arr[end])
            {
                return false;
            }
       
            // Update start
            start++;
       
            // If arr[end]
            // greater than arr[start]
            if (arr[end] > arr[start])
            {
                return false;
            }
       
            // Update end
            end--;
        }
       
        return true;
    }
 
  // Driver code
  static void Main()
  {
    int[] arr = { 1, 10, 14, 20, 18, 12, 5 };  
    int N = arr.Length;
   
    // Function Call
    if (isSpiralSorted(arr, N))
        Console.WriteLine("YES");
    else
        Console.WriteLine("NO");
  }
}
 
// This code is contributed bydivyesh072019

Javascript

    // Javascript program to implement
    // the above approach
     
    // Function to check if the array is
    // spirally sorted or not
    function isSpiralSorted(arr, n)
    {
        
        // Stores start index
        // of the array
        let start = 0;
        
        // Stores end index
        // of an array
        let end = n - 1;
        
        while (start < end)
        {
        
            // If arr[start]
            // greater than arr[end]
            if (arr[start] > arr[end])
            {
                return false;
            }
        
            // Update start
            start++;
        
            // If arr[end]
            // greater than arr[start]
            if (arr[end] > arr[start])
            {
                return false;
            }
        
            // Update end
            end--;
        }
        
        return true;
    }
     
    let arr = [ 1, 10, 14, 20, 18, 12, 5 ]; 
    let N = arr.length;
    
    // Function Call
    if (isSpiralSorted(arr, N))
        document.write("YES");
    else
        document.write("NO");
     

输出：

YES

时间复杂度： O(N)
辅助空间： O(1)