String Traversal and Character Access in DSA C - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of character traversal with pointer increment

What is the output of this C code snippet that traverses a string using a pointer?

DSA C

char *str = "hello";
char *p = str;
while (*p) {
    printf("%c-", *p);
    p++;
}
printf("null");

A h e l l o null

B h-e-l-l-o-

C hello-null

D h-e-l-l-o-null

💡 Hint

Remember that the loop prints each character followed by a dash until it reaches the null character.

The loop prints each character followed by a dash. After the loop ends, it prints 'null'. So the output is characters separated by dashes ending with 'null'.

❓ Predict Output

intermediate

Value of character after pointer arithmetic

Given the code below, what character is printed by the printf statement?

DSA C

char str[] = "world";
char *p = str + 2;
printf("%c", *p);

A l

B r

C o

D d

💡 Hint

Pointer p points to the third character in the string (index 2).

The string "world" has characters w(0), o(1), r(2), l(3), d(4). Pointer p points to index 2, which is 'r'.

🔧 Debug

advanced

Identify the error in string traversal loop

What error does this code produce when compiled and run?

DSA C

char *s = "test";
int i = 0;
while (s[i] != '\0') {
    printf("%c", s[0]);
    i--;
}

A Infinite loop printing 't'

B Compilation error

C Prints 'test' once and stops

D Segmentation fault

💡 Hint

Check how the index variable changes inside the loop.

The index i is decremented inside the loop, so it goes negative and s[i] never reaches '\0'. This causes an infinite loop printing the first character repeatedly.

❓ Predict Output

advanced

Output of nested loops accessing string characters

What is the output of this code snippet?

DSA C

char str[] = "abc";
for (int i = 0; i < 3; i++) {
    for (int j = 0; j <= i; j++) {
        printf("%c", str[j]);
    }
    printf("-");
}

A a-ab-abc-

B abc-abc-abc-

C a-aa-aaa-

D a-bc-abc-

💡 Hint

Inner loop prints characters from start up to current outer loop index.

For i=0, prints 'a'; i=1 prints 'ab'; i=2 prints 'abc'. Each followed by a dash.

🧠 Conceptual

expert

Number of characters printed by pointer loop

How many characters are printed by this code snippet?

DSA C

char *p = "data";
int count = 0;
while (*p++) {
    count++;
}
printf("%d", count);

A 3

B 5

C 4

D 0

💡 Hint

The loop counts characters until the null terminator is reached.

The string "data" has 4 characters before the null terminator. The loop increments count for each character until it reaches '\0'.