# Data Structure Questions and Answers – Length of a String using Recursion

This set of Data Structure Multiple Choice Questions & Answers (MCQs) focuses on “Length of a String using Recursion”.

1. Consider the following iterative implementation to find the length of the string:

```#include<stdio.h>
int get_len(char *s)
{
int len = 0;
while(________)
len++;
return len;
}
int main()
{
char *s = "harsh";
int len = get_len(s);
printf("%d",len);
return 0;
}```

Which of the following lines should be inserted to complete the above code?
a) s[len-1] != 0
b) s[len+1] != 0
c) s[len] != ‘\0’
d) s[len] == ‘\0’

Explanation: The line “s[len] != ‘\0′” should be inserted to complete the above code.

2. What is the output of the following code?

```#include<stdio.h>
int get_len(char *s)
{
int len = 0;
while(s[len] != '\0')
len++;
return len;
}
int main()
{
char *s = "lengthofstring";
int len = get_len(s);
printf("%d",len);
return 0;
}```

a) 14
b) 0
c) Compile time error
d) Runtime error

Explanation: The program prints the length of the string “lengthofstring”, which is 14.
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3. What is the time complexity of the following code used to find the length of the string?

```#include<stdio.h>
int get_len(char *s)
{
int len = 0;
while(s[len] != '\0')
len++;
return len;
}
int main()
{
char *s = "lengthofstring";
int len = get_len(s);
printf("%d",len);
return 0;
}```

a) O(1)
b) O(n)
c) O(n2)
d) O(logn)

Explanation: The time complexity of the code used to find the length of the string is O(n).

4. What is the output of the following code?

```#include<stdio.h>
int get_len(char *s)
{
int len = 0;
while(s[len] != '\0')
len++;
return len;
}
int main()
{
char *s = "";
int len = get_len(s);
printf("%d",len);
return 0;
}```

a) 0
b) 1
c) Runtime error
d) Garbage value

Explanation: The program prints the length of an empty string, which is 0.

5. Which of the following can be the base case for the recursive implementation used to find the length of a string?

```#include<stdio.h>
int get_len(char *s)
{
int len = 0;
while(s[len] != '\0')
len++;
return len;
}
int main()
{
char *s = "";
int len = get_len(s);
printf("%d",len);
return 0;
}```

a) if(string[len] == 1) return 1
b) if(string[len+1] == 1) return 1
c) if(string[len] == ‘\0’) return 0
d) if(string[len] == ‘\0’) return 1

Explanation: “if(string[len] == ‘\0’) return 0” can be used as base case in the recursive implementation used to find the length of the string.

6. Consider the following recursive implementation used to find the length of a string:

```#include<stdio.h>
int recursive_get_len(char *s, int len)
{
if(s[len] == 0)
return 0;
return ________;
}
int main()
{
char *s = "abcdef";
int len = recursive_get_len(s,0);
printf("%d",len);
return 0;
}```

Which of the following lines should be inserted to complete the above code?
a) 1
b) len
c) recursive_get_len(s, len+1)
d) 1 + recursive_get_len(s, len+1)

Explanation: The line “1 + recursive_get_len(s, len+1)” should be inserted to complete the code.

7. What is the output of the following code?

```#include<stdio.h>
int recursive_get_len(char *s, int len)
{
if(s[len] == 0)
return 0;
return 1 + recursive_get_len(s, len+1);
}
int main()
{
char *s = "abcdef";
int len = recursive_get_len(s,0);
printf("%d",len);
return 0;
}```

a) 5
b) 6
c) 7
d) 8

Explanation: The above code prints the length of the string “abcdef”, which is 6.

8. What is the time complexity of the following recursive implementation used to find the length of the string?

```#include<stdio.h>
int recursive_get_len(char *s, int len)
{
if(s[len] == 0)
return 0;
return 1 + recursive_get_len(s, len+1);
}
int main()
{
char *s = "abcdef";
int len = recursive_get_len(s,0);
printf("%d",len);
return 0;
}```

a) O(1)
b) O(n)
c) O(n2)
d) O(n3)

Explanation: The time complexity of the above recursive implementation used to find the length of the string is O(n).

9. How many times is the function recursive_get_len() called when the following code is executed?

```#include<stdio.h>
int recursive_get_len(char *s, int len)
{
if(s[len] == 0)
return 0;
return 1 + recursive_get_len(s, len+1);
}
int main()
{
int len = recursive_get_len(s,0);
printf("%d",len);
return 0;
}```

a) 6
b) 7
c) 8
d) 9

Explanation: The function recursive_get_len() is called 8 times when the above code is executed.

10. What is the output of the following code?

```#include<stdio.h>
int recursive_get_len(char *s, int len)
{
if(s[len] == 0)
return 0;
return 1 + recursive_get_len(s, len+1);
}
int main()
{
char *s = "123-1-2-3";
int len = recursive_get_len(s,0);
printf("%d",len);
return 0;
}```

a) 3
b) 6
c) 9
d) 10

Explanation: The above program prints the length of the string “123-1-2-3”, which is 9.

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