C Exercises: Count the number of triangles can be fromed from a given array
C Array: Exercise-52 with Solution
Write a program in C to count the number of triangles that can be formed from a given array.
Sample Solution:
C Code:
#include <stdio.h>
#include <stdlib.h>
int compare(const void* one, const void* two)
{
return *(int*)one > *(int*)two;
}
int CountNumberOfTriangles (int *arr1, int arr_size)
{
int ctrTriangle = 0, i, j, k;
qsort(arr1, arr_size, sizeof(int), compare);
for(i = 0; i < arr_size-2; ++i)
{
for (j = i+1; j < arr_size; ++j)
{
k = j +1;
while (k < arr_size && (arr1[i] + arr1[j])> arr1[k])
{
k++;
}
ctrTriangle += k - j - 1;
}
}
return ctrTriangle;
}
int main()
{
int arr1[] = {6, 18, 9, 7, 10};
int n = sizeof(arr1)/sizeof(arr1[0]);
int i;
//------------- print original array ------------------
printf("The given array is : ");
for(i = 0; i < n; i++)
{
printf("%d ", arr1[i]);
}
printf("\n");
//------------------------------------------------------
printf("Number of possible triangles can be formed from the array is: %d\n",
CountNumberOfTriangles(arr1, n));
return 0;
}
Sample Output:
The given array is : 6 18 9 7 10 Number of possible triangles can be formed from the array is: 5
Flowchart:

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Previous: Write a program in C to find the maximum circular subarray sum of a given array.
Next: Write a program in C to to print next greater elements in a given unsorted array. Elements for which no greater element exist, consider next greater element as -1.
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C Programming: Tips of the Day
C Programming - What is the argument for printf that formats a long?
Put an l (lowercased letter L) directly before the specifier.
unsigned long n; long m; printf("%lu %ld", n, m);
Ref : https://bit.ly/3dIwfkP
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