Description
Domo is a very smart dog. He also likes trolling people. One day, his teacher announced that only non-programmable calculators are allowed during the test, so he modified his non-programmable calculator into a programmable one. Knowing about his plan, you decided to give him a lesson by making it calculate prefix expressions instead of infix expressions.
Hint: Here are some functions you might want to use
int ungetc(int char, FILE *stream)
This is a function to return the character c to the stream. It is the opposite of int getc(FILE *stream). Try running this code for reference.
#include <stdio.h>
int main() {
double f;
char c;
//to get the character c from the input stream
c = getc(stdin);
//uncomment the function below and see what will happen
//ungetc(c, stdin);
scanf("%lf", &f);
printf("char: %c\ndouble: %lf\n", c, f);
}
double atof(const char *str)
This is a function for converting a string str to a double-precision floating point. It is included in the <stdlib.h>.
#include <stdio.h>
#include <stdlib.h>
int main() {
//this is a string
char flt[] = "3.141593";
//now this is a double
printf("%lf", atof(flt));
}
Input
There will be only one line of an expression in prefix notation, which contains no more than 10,000 non-negative double-precision floats and operators +, -, *, or /. There will be a space after every number and operator.
Output
The result of calculation in 4 decimal place precision with a trailing '\n'. You can use %.4lf to achieve this.