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cfunctionintegerchecksum

Why does the program gives wrong output?

Checksum of a number is the sum of all its digits.
I wrote the following program to find the checksum of a number:

#include <stdio.h>

int read(){
    int read;
    printf("number between 1000 and 100.000: ");
    scanf("%d", &read);
    return read;
}
int calcSum(int num){
    int a;
    if (num < 10)
       return num;
    a = calcSum (num / 10) + num % 10;
    if (a > 10)
        a += calcSum (a / 10) + a % 10;
    return a;
}
void output(int in, int num){
    printf("checksum vof %d = %d", in, num);
}
int main(){
    int num;
    num = read();
    output(num, calcSum(num));
    return 0;
}

It works with some numbers like 11, 12 but not with numbers like 706

Solution

  • If a > 10, you are performing the same operation multiple times. Just do:

    int calcSum(int num) {
    int a;
    if (num < 10)
       return num;
    a = calcSum (num / 10) + num % 10;
    return a;
}