检查数组是否是双调的程序

给定一个包含 N 个元素的数组。任务是检查阵列是否是双调的。
如果数组中的元素首先严格增加然后严格减少，则称该数组是双调的。
例子：

Input: arr[] = {-3, 9, 11, 20, 17, 5, 1}
Output: YES

Input: arr[] = {5, 6, 7, 8, 9, 10, 1, 2, 11};
Output: NO

方法：

开始遍历数组并继续检查下一个元素是否大于当前元素。
如果在任何时候，下一个元素不大于当前元素，则中断循环。
再次从当前元素开始遍历并检查下一个元素是否小于当前元素。
如果在到达数组末尾之前的任何点，如果下一个元素不小于当前元素，则中断循环并打印 NO。
如果成功到达数组末尾，则打印 YES。

以下是上述方法的实现：

C++

// C++ program to check if an array is bitonic
#include 
using namespace std;
 
// Function to check if the given array is bitonic
int checkBitonic(int arr[], int n)
{
    int i, j;
 
    // Check for increasing sequence
    for (i = 1; i < n; i++) {
        if (arr[i] > arr[i - 1])
            continue;
 
        if (arr[i] <= arr[i - 1])
            break;
    }
 
    if (i > n - 1)
        return 1;
 
    // Check for decreasing sequence
    for (j = i + 1; j < n; j++) {
        if (arr[j] < arr[j - 1])
            continue;
 
        if (arr[j] >= arr[j - 1])
            break;
    }
 
    i = j;
 
    if (i != n)
        return 0;
 
    return 1;
}
 
// Driver code
int main()
{
    int arr[] = { 1,2,3 };
 
    int n = sizeof(arr) / sizeof(arr[0]);
 
    (checkBitonic(arr, n) == 1) ? cout << "YES"
                                : cout << "NO";
 
    return 0;
}

Java

// Java program to check
// if an array is bitonic
class GFG
{
// Function to check if the
// given array is bitonic
static int checkBitonic(int arr[], int n)
{
    int i, j;
 
    // Check for increasing sequence
    for (i = 1; i < n; i++)
    {
        if (arr[i] > arr[i - 1])
            continue;
 
        if (arr[i] <= arr[i - 1])
            break;
    }
 
    if (i == n - 1)
        return 1;
 
    // Check for decreasing sequence
    for (j = i + 1; j < n; j++)
    {
        if (arr[j] < arr[j - 1])
            continue;
 
        if (arr[j] >= arr[j - 1])
            break;
    }
 
    i = j;
 
    if (i != n)
        return 0;
 
    return 1;
}
 
// Driver Code
public static void main(String args[])
{
    int arr[] = { -3, 9, 7, 20, 17, 5, 1 };
 
    int n = arr.length;
 
    System.out.println((checkBitonic(arr, n) == 1) ?
                                             "YES" : "NO");
}
}
 
// This code is contributed by Bilal

Python3

# Python3 program to check if
# an array is bitonic or not.
 
# Function to check if the
# given array is bitonic
def checkBitonic(arr, n) :
 
    # Check for increasing sequence
    for i in range(1, n) :
        if arr[i] > arr[i - 1] :
            continue
        else :
            break
 
    if i == n-1 :
        return 1
 
    # Check for decreasing sequence
    for j in range(i + 1, n) :
         
        if arr[j] < arr[j - 1] :
            continue
        else :
            break
 
    i = j
    if i != n - 1 :
        return 0
 
    return 1
 
# Driver Code
if __name__ == "__main__" :
     
    arr = [-3, 9, 7, 20, 17, 5, 1]
     
    n = len(arr)
 
    if checkBitonic(arr, n) == 1 :
        print("YES")
    else :
        print("NO")
 
# This code is contributed
# by ANKITRAI1

C#

// C# program to check
// if an array is bitonic
using System;
 
class GFG
{
// Function to check if the
// given array is bitonic
static int checkBitonic(int []arr,
                        int n)
{
    int i, j;
 
    // Check for increasing sequence
    for (i = 1; i < n; i++)
    {
        if (arr[i] > arr[i - 1])
            continue;
 
        if (arr[i] <= arr[i - 1])
            break;
    }
 
    if (i == n - 1)
        return 1;
 
    // Check for decreasing sequence
    for (j = i + 1; j < n; j++)
    {
        if (arr[j] < arr[j - 1])
            continue;
 
        if (arr[j] >= arr[j - 1])
            break;
    }
 
    i = j;
 
    if (i != n)
        return 0;
 
    return 1;
}
 
// Driver Code
public static void Main()
{
    int []arr = { -3, 9, 7, 20, 17, 5, 1 };
 
    int n = arr.Length;
 
    Console.WriteLine((
            checkBitonic(arr, n) == 1) ?
                                 "YES" : "NO");
}
}
 
// This code is contributed by Bilal

PHP

 $arr[$i - 1])
            continue;
 
        if ($arr[$i] <= $arr[$i - 1])
            break;
    }
 
    if ($i == $n - 1)
        return 1;
 
    // Check for decreasing sequence
    for ($j = $i + 1; $j < $n; $j++)
    {
        if ($arr[$j] < $arr[$j - 1])
            continue;
 
        if ($arr[$j] >= $arr[$j - 1])
            break;
    }
 
    $i = $j;
 
    if ($i != $n)
        return 0;
 
    return 1;
}
 
// Driver code
$arr = array( -3, 9, 7, 20, 17, 5, 1 );
 
$n = sizeof($arr);
 
checkBitonic($arr, $n) == 1 ?
               print("YES") : print("NO");
 
// This code is contributed by ChitraNayal
?>

Javascript

输出：

NO