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POmerging two strings together in C, switching off characters
 

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  1. POmerging two strings together in C, switching off characters
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    <p>I am trying to merge two strings of variable length in C. The result should be 1st character from str1 then 1st character from str2 then 2nd character from str1, 2nd character from str2, etc. When it reaches the end of one string it should append the rest of the other string.</p> <p>For Example:</p> <pre><code>str1 = "abcdefg"; str2 = "1234"; outputString = "a1b2c3d4efg"; </code></pre> <p>I'm pretty new to C, my first idea was to convert both strings to arrays then try to iterate through the arrays but I thought there might be an easier method. Sample code would be appreciated.</p> <p><strong>UPDATE:</strong> I've tried to implement the answer below. My function looks like the following.</p> <pre><code>void strMerge(const char *s1, const char *s2, char *output, unsigned int ccDest) { printf("string1 is %s\n", s1); printf("string2 is %s\n", s2); while (*s1 != '\0' &amp;&amp; *s2 != '\0') { *output++ = *s1++; *output++ = *s2++; } while (*s1 != '\0') *output++ = *s1++; while (*s2 != '\0') *output++ = *s2++; *output = '\0'; printf("merged string is %s\n", *output); } </code></pre> <p>But I get a warning when compiling:</p> <pre><code>$ gcc -g -std=c99 strmerge.c -o strmerge strmerge2.c: In function ‘strMerge’: strmerge2.c:41:5: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘int’ [-Wformat] </code></pre> <p>And when I run it it doesnt work:</p> <pre><code>./strmerge abcdefg 12314135 string1 is abcdefg string2 is 12314135 merged string is (null) </code></pre> <p>Why does it think argument 2 is an int and how do I fix it to be a char? If I remove the "*" off output in the printf it doesn't give a compile error but the function still doesn’t work.</p>
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    1. COSo what is your actual problem?
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    2. COA user types in two strings. I need to return a single string that is a merge of the two strings.
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      1. UStbenz9
    3. COOne of your problems is space management — where is the output going to be placed. With that done, the code is fairly straight-forward. While neither input string is finished, copy a character from each to the output. Once one is finished, you have two more loops to run, one to exhaust the first string and the other to exhaust the second string. Only one of those will be executed (depending on which string is longer), but don't bother trying to find out which it is; there's no need (assuming you write the loops correctly).
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      1. USJonathan Leffler
 

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