int test_ex_1_1_18(int argc, const char * argv[]) {
int a = 2, b = 25, m = 3, n = 11;;
printf("%d\n", mystery(a, b));
printf("%d\n", mystery(m, n));
printf("%d\n", mystery2(a, b));
printf("%d\n", mystery2(m, n));
return 0;
}
/*
a的倍数增加方式（偶数时增加一倍，奇数时增加一倍，再加1），类似于b的递减（偶数时减少一半，奇数时减1后，再减少一半），所以最终mystery(a, b) = a * b
*/
int mystery(int a, int b) {
if (b == 0) {
return 0;
}
if (b % 2 == 0) {
return mystery(a + a, b / 2);
}
return mystery(a + a, b / 2) + a;
}
/* multiplies a for b times recursively */
int mystery(int a, int b)
{
if(b == -1)
return -a;
else if(b == 1)
return a;
else {
if(b > 1)
return a + mystery(a, b - 1);
else
return -a + mystery(a, b + 1);
}
} /* eof mystery() */
int main()
{
int x, y;
printf("Enter two integers: ");
scanf("%d%d", &x, &y);
printf("The result is %d\n", mystery(x, y));
return 0;
} /* E0F main */
int main() {
/* sample run */
unsigned int n = 305419896;
unsigned char c = 171;
printf("sizeof(unsigned int) = %lu \n\n", sizeof(unsigned int));
printf("sizeof(unsigned char) = %lu \n\n", sizeof(unsigned char));
unsigned result = mystery(n, 2, c);
printf("%u ===> %u\n", n, result);
return 0;
}
int main() { mystery(); }
