I know that this may be a dumb question, but I am still learning C so I don't know all the nuances.

Basically the gist of my question is that say I have the separate integers 1, 3 and 2. I want to add 2 to 1 that makes it 21. I know I could do 2*10, then add 1. Then add 3 to the beginning making it 321. Basically I need to add one number to the beginning of another number multiple times. Sadly, I cannot use the pow function for this.

Let me know if you need me to explain it anymore.

CodePudding user response：

There is many ways you can do this.

If you can't use the pow function why not make your own?

Here is one way I thought of doing this. I hope this can inspire you to come up with your own way.

If you need more then 10 digits you would have to use long instead of int.

#include <stdio.h>


int notpow(int y) {
    int ans = 10;
    if (y == 0) {
        return 1;
    }
    for (int i = 1; i < y; i  ) {
        ans *= 10;
    }
    return ans;
}


int main() {
    // //Basic idea
    int num1 = 1;
    int num2 = 3;
    int num3 = 2;
    int ans = 0;
    ans = num1*notpow(2)   num2 *notpow(1)   num3*notpow(0);
    printf("ans = %i\n", ans);
    //For n numbers
    int howMany, howManyCount = 1;
    printf("How many digits?: ");
    scanf("%d",&howMany);
    int temp = 0;
    int countDown = howMany-1;
    ans = 0;
    printf("\n");
    for (int i = 0; i < howMany; i  ) {
        printf("Enter digit %i: ", (i 1));
        scanf("%d",&temp);
        printf("\n");
        ans = ans   temp*notpow(countDown--);
        printf("ans = %i\n", ans);
    }
    printf("Final ans = %i\n", ans);
    return 0;
}

CodePudding user response：

Well, you can try out this program.

#include <stdio.h>
#include <string.h>

int power(int base, int exp) {
    int res = 1;
    while (exp > 0) {
        res *= base;
        exp--;
    }

    return res;
}

int main() {
    int someNumber = 7, length, numToAdd = 3;
    char string[10];
    sprintf(string, "%d", someNumber);
    length = strlen(string);
    someNumber = numToAdd * power(10, length)   someNumber;
    printf("%d\n", someNumber);
}

I hope the code is self explanatory.