Interleaving of two given strings with no common characters

#include <bits/stdc++.h>
using namespace std;

// Returns true if s3 is an interleaving of s1 and s2
bool isIL(string& s1, string& s2, string& s3) {
  
    int i = 0, j = 0;
  
    if (s1.size() + s2.size() != s3.size())
        return false;
    
    // Iterate through all characters of s3
    for (int k = 0; k < s3.size(); k++) {
      
        // Match the current character of s3 with the 
        // current character of s1. If they match, 
        // move s1 to the next character.
        if (i < s1.size() && s1[i] == s3[k]) {
            i++;
        } 
      
        // Else match the current character of s3 
        // with the current character of s2.
        // If they match, move s2 to the next character.
        else if (j < s2.size() && s2[j] == s3[k]) {
            j++;
        } 
      
        // If it doesn't match with either s1 or s2, 
        // return false
        else {
            return false;
        }
    }
    
    // If all characters of s3 match with either
    // s1 or s2.
    return true;
}

int main() {
    string s1 = "AB";
    string s2 = "CD";
    string s3 = "ACBD";
    
    if (isIL(s1, s2, s3)) {
        cout << s3 << " is interleaved of " << s1 << " and " << s2;
    } else {
        cout << s3 << " is not interleaved of " << s1 << " and " << s2;
    }

    return 0;
}

// C program to check if given string is an interleaving
// of the other two strings
#include<stdio.h>

// Returns true if C is an interleaving of A and B,
// otherwise returns false
bool isInterleaved (char *A, char *B, char *C)
{
    // Iterate through all characters of C.
    while (*C != 0)
    {
        // Match first character of C with first character
        // of A. If matches them move A to next 
        if (*A == *C)
            A++;

        // Else Match first character of C with first 
        // character of B. If matches them move B to next 
        else if (*B == *C)
            B++;
 
        // If doesn't match with either A or B, then return
        // false
        else
            return false;
        
        // Move C to next for next iteration
        C++;
    }

    // If A or B still have some characters, then length of
    // C  is smaller than sum of lengths of A and B, so 
    // return false
    if (*A || *B)
        return false;

    return true;
}

// Driver program to test above functions
int main()
{
    char *A = "AB";
    char *B = "CD";
    char *C = "ACBG";
    if (isInterleaved(A, B, C) == true)
        printf("%s is interleaved of %s and %s", C, A, B);
    else
        printf("%s is not interleaved of %s and %s", C, A, B);

    return 0;
}

// This code is contributed by Venkat