To find the next greater element in an array

Question:

Find the next greater element for each element in the given array.

Logic:

• First, check for the element which is greater than a[i].
• If greater element found means stores into a variable m.
• If any elements greater than a[i] and less than m.
• Then reassign m with the greater element which is found.
• Otherwise, it is the largest element of the array and it has no greater elements.
• Print all the elements with their corresponding greater element.

Program:

#include<stdio.h>
void main()
{
    int a[20],i,j,n,m,l=1;
    clrscr();
    printf("enter the length:");
    scanf("%d",&n);
    printf("enter the elements:\n");
    for(i=0;i<n;i++)
    {
        scanf("%d",&a[i]);
    }
    for(i=0;i<n;i++)
    {
        for(j=0;j<n;j++)
        {
            if(a[i]<a[j]&&l==1)             //checks for the greater element
            {
                l=0;
                m=a[j];                     //assign greater element to m
            }
            else if(a[i]<a[j]&&a[j]<m) //checks for least greater number 
	    { 
		m=a[j]; 
	    } 
	} 
	if(l!=1) //next grater element found 
	{ 
	printf("%d->%d\n",a[i],m);
        }
        else                                //when no elements greater than a[i]
        {
            printf("%d->_\n",a[i]);
        }
        l=1;                                //acts as a marker for identifying it as greater element or not
    }
    getch();
}

Alternate way:

An alternate way is to sort all the elements in ascending or descending order then print the next element which is the next greater element.

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