Question

How to add leading zeros to the shorter string of two strings in C++

Answer 1

#include <iostream>
#include <string>
#include <cmath>

std::string addLeadingZero(std::string str1, std::string str2) {
    int len1 = str1.length();
    int len2 = str2.length();

    std::string strToPad = "";

    int diff = std::abs(len1 - len2);

    if (diff > 0) {
        strToPad = std::string(diff, '0') + (len1 > len2 ? str2 : str1);
    }

    return strToPad;
}

int main(int argc, char* argv[]) {
    std::string str1 = "123";
    std::string str2 = "8976753";

    if (str1.length() > str2.length()) {
        str2 = addLeadingZero(str1, str2);
    }
    else {
        str1 = addLeadingZero(str1, str2);
    }

    std::cout << str1 << std::endl;
    std::cout << str2 << std::endl;
}





/*
run:

0000123
8976753

*/

 

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Answer 2

#include <iostream>
#include <cstring>
 
void addLeadingZero(char* str1, char* str2) {
    size_t len1 = strlen(str1);
    size_t len2 = strlen(str2);
 
    char* str_to_pad = len1 > len2 ? str2 : str1;
 
    size_t diff = len1 > len2 ? (len1 - len2) : (len2 - len1);
 
    if (diff) {
        std::memmove(str_to_pad + diff, str_to_pad, len1 > len2 ? len2 + 1 : len1 + 1);
        std::memset(str_to_pad, '0', diff);
    }
}
 
int main()
{
    char str1[32] = "123";
    char str2[32] = "8976753";
 
    addLeadingZero(str1, str2);
 
    std::cout << str1 << std::endl;
    std::cout << str2 << std::endl;
}
 
  
  
  
/*
run:
  
0000123
8976753
  
*/

 

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