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Law of cosines - triples: Difference between revisions
→{{header|C}}
Line 113:
=={{header|C}}==
=== O(N^2) ===
<lang C>/*
* RossetaCode: Law of cosines - triples
Line 162 ⟶ 163:
gamma = 60 degrees, a*a + b*b - a*b == c*c, number of triangles = 2
gamma = 120 degrees, a*a + b*b + a*b == c*c, number of triangles = 15
</pre>
=== O(N^3) ===
<lang C>/*
* RossetaCode: Law of cosines - triples
*
* A solutions with O(N^2) cost.
*/
#include <stdio.h>
#include <math.h>
#define MAX_SIDE_LENGTH 10000
//#define DISPLAY_TRIANGLES
int main(void)
{
static char description[3][80] = {
"gamma = 90 degrees, a*a + b*b == c*c",
"gamma = 60 degrees, a*a + b*b - a*b == c*c",
"gamma = 120 degrees, a*a + b*b + a*b == c*c"
};
static int coeff[3] = { 0, -1, 1 };
printf("MAX SIDE LENGTH = %d\n\n", MAX_SIDE_LENGTH);
for (int k = 0; k < 3; k++)
{
int counter = 0;
for (int a = 1; a <= MAX_SIDE_LENGTH; a++)
for (int b = 1; b <= a; b++)
{
int cc = a * a + b * b - coeff[k] * a * b;
int c = (int)(sqrt(cc) + 0.5);
if (c <= MAX_SIDE_LENGTH && c * c == cc)
{
#ifdef DISPLAY_TRIANGLES
printf("%d %d %d\n", a, b, c);
#endif
counter++;
}
}
printf("%s, number of triangles = %d\n", description[k], counter);
}
return 0;
}
</lang>
{{output}}
<pre>
MAX SIDE LENGTH = 10000
gamma = 90 degrees, a*a + b*b == c*c, number of triangles = 12471
gamma = 60 degrees, a*a + b*b - a*b == c*c, number of triangles = 10374
gamma = 120 degrees, a*a + b*b + a*b == c*c, number of triangles = 28394
</pre>
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