#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[] = {7, 15, 6, 3, 11};
int n = sizeof(arr1) / sizeof(arr1[0]);
int i;
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;
}
OUTPUT:
The given array is : 7 15 6 3 11
Number of possible triangles can be formed from the array is: 4