int sum_of_powers(int sum, int power, int no)
{
int remaining_sum = sum - pow(no, power);
if (remaining_sum < 0) {
return 0;
} else if (remaining_sum == 0) {
return 1;
} else {
return sum_of_powers(remaining_sum, power, no+1) + //include no
sum_of_powers(sum, power, no+1); //exclude no
}
}
int main()
{
int X, n;
int *d = NULL;
scanf("%d", &X);
scanf("%d", &n);
printf("%d\n", sum_of_powers(X, n, 1));
}
/*
Main method gets the user's command and recognizes one of three options:
quit, help, <n>
<n> is any positive value the user enters into the console. The sum_of_powers() method will uses n
in its parameters and calculate base n to power n starting from value n and subsiquently decreasing
n by 1 at each summand until the value of n equals 1.
*/
int main()
{
printf("Enter \"help\" for a list of commands\n");
while(1)
{
char input[10];
int valid_character = 0;
int i;
while(valid_character == 0)
{
printf("Please enter a command: ");
fgets(input, 20, stdin);
for(i = 0; i < strlen(input) - 1; i++)
{
if(input[i] == ' ')
valid_character = 1;
else if(input[i] >= 'a' && input[i] <= 'z')
{
input[i] = input[i] - 'a' + 'A';
valid_character = 1;
}
else if(input[i] >= 'A' && input[i] <= 'Z' || input[i] >= '0' && input[i] <= '9')
valid_character = 1;
else
{
valid_character = 0;
printf("\nYou entered an invalid entry!\n");
printf("You entered an invalid character.\n\n");
printf("Enter \"help\" for a list of commands\n");
break;
}
}
}
//The user entered "quit"
if(input[0] == 'Q' && input[1] == 'U' && input[2] == 'I' && input[3] == 'T')
{
printf("\n*******************************************************************************\n");
printf("Thanks for using this sum of powers application!\n");
printf("*******************************************************************************\n");
return 0;
}
//The user entered "help"
else if(input[0] == 'H' && input[1] == 'E' && input[2] == 'L' && input[3] == 'P')
{
printf("\n*******************************************************************************\n");
printf("[quit]\n");
printf("Terminates execution.\n\n");
printf("[help]\n");
printf("Prints a short help doc to the terminal.\n\n");
printf("[<n>]\n");
printf("<n> is a positive number. The command will print out the sum of base n to\n");
printf("power n with the starting value of n by 1 at each summand until the value n\n");
printf("equals 1.\n");
printf("*******************************************************************************\n\n");
}
//The user entered a number <n>
else if(input[0] >= '0' && input[0] <= '9')
{
int n;
int valid_format = 0;
//The following loop uses three flags to make sure the entire input entry is valid
//valid_format checks to see if '0' to '9', ',' was entered
n = 0;
for(i = 0; i < strlen(input) - 1; i++)
{
if(input[i] >= '0' && input[i] <= '9')
valid_format = 1;
else
{
valid_format = 0;
printf("\nYou entered an invalid entry!\n");
printf("Positive numbers are only allowed.\n");
break;
}
}
n = atoi(input);
if(valid_format == 1)
{
int count = n;
printf("\n");
while(count > 1)
{
printf("%d^%d + ", count, count);
count--;
}
printf("%d^%d = ", count, count);
printf("%d\n", sum_of_powers(n));
printf("\n");
}
}
//The user entered an invalid command
else
{
printf("You entered an invalid command!\n\n");
printf("Enter \"help\" for a list of commands\n");
}
}
}
