執行時間測量(gcd)

#include <time.h>

#include <iostream>

#include <math.h>

#include <algorithm>

using namespace std;

int gcd1(int a, int b){

     for (int d = 1; d <= min(a, b); d++){

         if (a%d == 0 && b%d == 0) return d;

     }

}

int gcd2(int a, int b){

     if (a<b) swap(a, b);

     if (a%b)

         return b;

     else

         return gcd2(a - b, b);

}

// source: http://www.math.wustl.edu/~victor/mfmm/compaa/gcd.c

/* Standard C Function: Greatest Common Divisor */

int gcd(int a, int b)

{

     int c;

     while (a != 0) {

         c = a; a = b%a;  b = c;

     }

     return b;

}

/* Recursive Standard C Function: Greatest Common Divisor */

int gcdr(int a, int b)

{

     if (a == 0) return b;

     return gcdr(b%a, a);

}

void main(){

     clock_t begin = clock();

     // your CODE

     srand(clock());

     int x = rand();

     int y = rand();

     for (int i = 0; i < 100000000; i++){

         gcd1(x, y);

     }

     clock_t end = clock();  

     cout << end - begin;

     //system("pause");

}