[C language] Leetcode — 1768. Merge Strings Alternately

You are given two strings word1 and word2. Merge the strings by adding letters in alternating order, starting with word1. If a string is longer than the other, append the additional letters onto the end of the merged string.

Return the merged string.

 

Example 1:

Input: word1 = "abc", word2 = "pqr"
Output: "apbqcr"
Explanation: The merged string will be merged as so:
word1:  a   b   c
word2:    p   q   r
merged: a p b q c r

Example 2:

Input: word1 = "ab", word2 = "pqrs"
Output: "apbqrs"
Explanation: Notice that as word2 is longer, "rs" is appended to the end.
word1:  a   b 
word2:    p   q   r   s
merged: a p b q   r   s

Example 3:

Input: word1 = "abcd", word2 = "pq"
Output: "apbqcd"
Explanation: Notice that as word1 is longer, "cd" is appended to the end.
word1:  a   b   c   d
word2:    p   q 
merged: a p b q c   d

 

 

Answer

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

char * mergeAlternately(char * word1, char * word2){
    int len1 = strlen(word1);
    int len2 = strlen(word2);

    int resultLen = len1 + len2 + 1;
    
    //malloc: memory allocation
    //<stdlib.h> required to use malloc
    //resultLen is len1+len2+1 byte allocated
    char * result = (char*)malloc(resultLen);

    int i =0, j=0, k=0;

    while(i < len1 && j < len2){
        result[k++] = word1[i++];
        result[k++] = word2[j++];
    }

    while(i<len1){
        result[k++] = word1[i++];
    }

    while(j<len2){
        result[k++] = word2[j++];
    }

    result[k] = '\0';

    return result;

    free(mergeAlternately);
}

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

char * mergeAlternately(char * word1, char * word2){
    size_t len1 = strlen(word1);
    size_t len2 = strlen(word2);

    //malloc: memory allocation
    char * result = (char*) malloc(sizeof(char) * (len1 + len2 + 1));

    size_t i = 0, j = 0, k = 0;

    for(i = 0, j = 0, k = 0; i < len1 || j < len2; i++, j++){
        if(i <len1){
            result[k++] = word1[i];
        }
        if(j<len2){
            result[k++] = word2[j];
        }
    }
    result[k] = '\0';
    return result;
}