I tried "x = y ** e", but that didn't work.
This question is related to
c
or you could just write the power function, with recursion as a added bonus
int power(int x, int y){
if(y == 0)
return 1;
return (x * power(x,y-1) );
}
yes,yes i know this is less effecient space and time complexity but recursion is just more fun!!
To add to what Evan said: C does not have a built-in operator for exponentiation, because it is not a primitive operation for most CPUs. Thus, it's implemented as a library function.
Also, for computing the function e^x, you can use the exp(double)
, expf(float)
, and expl(long double)
functions.
Note that you do not want to use the ^
operator, which is the bitwise exclusive OR operator.
pow
only works on floating-point numbers (double
s, actually). If you want to take powers of integers, and the base isn't known to be an exponent of 2
, you'll have to roll your own.
Usually the dumb way is good enough.
int power(int base, unsigned int exp) {
int i, result = 1;
for (i = 0; i < exp; i++)
result *= base;
return result;
}
Here's a recursive solution which takes O(log n)
space and time instead of the easy O(1)
space O(n)
time:
int power(int base, int exp) {
if (exp == 0)
return 1;
else if (exp % 2)
return base * power(base, exp - 1);
else {
int temp = power(base, exp / 2);
return temp * temp;
}
}
The non-recursive version of the function is not too hard - here it is for integers:
long powi(long x, unsigned n)
{
long p = x;
long r = 1;
while (n > 0)
{
if (n % 2 == 1)
r *= p;
p *= p;
n /= 2;
}
return(r);
}
(Hacked out of code for raising a double value to an integer power - had to remove the code to deal with reciprocals, for example.)
int power(int x,int y){
int r=1;
do{
r*=r;
if(y%2)
r*=x;
}while(y>>=1);
return r;
};
(iterative)
int power(int x,int y){
return y?(y%2?x:1)*power(x*x,y>>1):1;
};
(if it has to be recursive)
imo, the algorithm should definitely be O(logn)
The non-recursive version of the function is not too hard - here it is for integers:
long powi(long x, unsigned n)
{
long p = x;
long r = 1;
while (n > 0)
{
if (n % 2 == 1)
r *= p;
p *= p;
n /= 2;
}
return(r);
}
(Hacked out of code for raising a double value to an integer power - had to remove the code to deal with reciprocals, for example.)
or you could just write the power function, with recursion as a added bonus
int power(int x, int y){
if(y == 0)
return 1;
return (x * power(x,y-1) );
}
yes,yes i know this is less effecient space and time complexity but recursion is just more fun!!
Similar to an earlier answer, this will handle positive and negative integer powers of a double nicely.
double intpow(double a, int b)
{
double r = 1.0;
if (b < 0)
{
a = 1.0 / a;
b = -b;
}
while (b)
{
if (b & 1)
r *= a;
a *= a;
b >>= 1;
}
return r;
}
The non-recursive version of the function is not too hard - here it is for integers:
long powi(long x, unsigned n)
{
long p = x;
long r = 1;
while (n > 0)
{
if (n % 2 == 1)
r *= p;
p *= p;
n /= 2;
}
return(r);
}
(Hacked out of code for raising a double value to an integer power - had to remove the code to deal with reciprocals, for example.)
To add to what Evan said: C does not have a built-in operator for exponentiation, because it is not a primitive operation for most CPUs. Thus, it's implemented as a library function.
Also, for computing the function e^x, you can use the exp(double)
, expf(float)
, and expl(long double)
functions.
Note that you do not want to use the ^
operator, which is the bitwise exclusive OR operator.
Similar to an earlier answer, this will handle positive and negative integer powers of a double nicely.
double intpow(double a, int b)
{
double r = 1.0;
if (b < 0)
{
a = 1.0 / a;
b = -b;
}
while (b)
{
if (b & 1)
r *= a;
a *= a;
b >>= 1;
}
return r;
}
To add to what Evan said: C does not have a built-in operator for exponentiation, because it is not a primitive operation for most CPUs. Thus, it's implemented as a library function.
Also, for computing the function e^x, you can use the exp(double)
, expf(float)
, and expl(long double)
functions.
Note that you do not want to use the ^
operator, which is the bitwise exclusive OR operator.
The non-recursive version of the function is not too hard - here it is for integers:
long powi(long x, unsigned n)
{
long p = x;
long r = 1;
while (n > 0)
{
if (n % 2 == 1)
r *= p;
p *= p;
n /= 2;
}
return(r);
}
(Hacked out of code for raising a double value to an integer power - had to remove the code to deal with reciprocals, for example.)
To add to what Evan said: C does not have a built-in operator for exponentiation, because it is not a primitive operation for most CPUs. Thus, it's implemented as a library function.
Also, for computing the function e^x, you can use the exp(double)
, expf(float)
, and expl(long double)
functions.
Note that you do not want to use the ^
operator, which is the bitwise exclusive OR operator.
pow
only works on floating-point numbers (double
s, actually). If you want to take powers of integers, and the base isn't known to be an exponent of 2
, you'll have to roll your own.
Usually the dumb way is good enough.
int power(int base, unsigned int exp) {
int i, result = 1;
for (i = 0; i < exp; i++)
result *= base;
return result;
}
Here's a recursive solution which takes O(log n)
space and time instead of the easy O(1)
space O(n)
time:
int power(int base, int exp) {
if (exp == 0)
return 1;
else if (exp % 2)
return base * power(base, exp - 1);
else {
int temp = power(base, exp / 2);
return temp * temp;
}
}
or you could just write the power function, with recursion as a added bonus
int power(int x, int y){
if(y == 0)
return 1;
return (x * power(x,y-1) );
}
yes,yes i know this is less effecient space and time complexity but recursion is just more fun!!
int power(int x,int y){
int r=1;
do{
r*=r;
if(y%2)
r*=x;
}while(y>>=1);
return r;
};
(iterative)
int power(int x,int y){
return y?(y%2?x:1)*power(x*x,y>>1):1;
};
(if it has to be recursive)
imo, the algorithm should definitely be O(logn)
or you could just write the power function, with recursion as a added bonus
int power(int x, int y){
if(y == 0)
return 1;
return (x * power(x,y-1) );
}
yes,yes i know this is less effecient space and time complexity but recursion is just more fun!!
pow
only works on floating-point numbers (double
s, actually). If you want to take powers of integers, and the base isn't known to be an exponent of 2
, you'll have to roll your own.
Usually the dumb way is good enough.
int power(int base, unsigned int exp) {
int i, result = 1;
for (i = 0; i < exp; i++)
result *= base;
return result;
}
Here's a recursive solution which takes O(log n)
space and time instead of the easy O(1)
space O(n)
time:
int power(int base, int exp) {
if (exp == 0)
return 1;
else if (exp % 2)
return base * power(base, exp - 1);
else {
int temp = power(base, exp / 2);
return temp * temp;
}
}
Source: Stackoverflow.com