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Heads Up! Please don’t learn this table by heart. This is just to check your understanding and you should know how these complexities came

Algorithm	Worst Case	Average Case	Best Case	Min. no. of swaps	Max. no. of swaps
Bubble	$\Theta(n^{2})$	$\Theta(n^{2})$	$\Theta(n)$	0	$\Theta(n^{2})$
Selection	$\Theta(n^{2})$	$\Theta(n^{2})$	$\Theta(n^{2})$	0	$\Theta(n)$
Insertion	$\Theta(n^{2})$	$\Theta(n^{2})$	$\Theta(n)$	0	$\Theta(n^{2})$
Quick	$\Theta(n^{2})$	$\Theta(n\lg n)$	$\Theta(n\lg n)$	0	$\Theta(n^{2})$
Merge	$\Theta(n\lg n)$	$\Theta(n\lg n)$	$\Theta(n\lg n)$	Is not in-place sorting	Is not in-place sorting
Heap	$\Theta(n\lg n)$	$\Theta(n\lg n)$	$\Theta(n\lg n)$	$O(n\lg n)$	$\Theta(n\lg n)$

The best case for insertion sort happens when the input array is already sorted. Each new element will then be put at the end of the array and the complexity will be $\Theta(n)$.
Interestingly, the worst case for quick sort also happens when the input array is sorted (either ascending or descending). This happens only if we choose the pivot as either the first element or the last element. In either of these case, we split the array across the pivot with n-1 elements on one array and just 1 element on the other array, which makes the complexity go to $\Theta(n^2)$

missinglatex

In-Place Sorting

When sorting happens within the same array, its called in-place sorting. All the above sorting algorithms except merge sort are in-place sorting. In merge sort, we use an auxiliary array for merging two sub-arrays and hence its not in-place sorting.

Stable sorting

This matters only for arrays with some element(s) repeated. If $A[x] = A[y]$, in the original array such that $x<y$, then in the sorted array, $A[x]$ must be placed at position $u$ and $A[y]$ must be placed at position $v$, such that $u < v$. i.e.; the relative positions of same value elements must be same in the sorted array as in the input array, for the sorting algorithm to be stable. In most cases stability depends on the way in which algorithm is implemented. Still, its not possible to implement heap sort as a stable sort.

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Consider the following program:

#include <stdio.h> int main() { int a[10][20][30]={0}; printf("%ld",&a+1 - &a); return 0; }

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#include <stdio.h>
int main()
{
    int a[10][20][30]={0};
    printf("%ld",&a+1 - &a);

    return 0;
}

What is the output of this program?

Consider the following program:

#include <stdio.h> 
int main()
{
    int a[10][20][30] = {0};
    int *b = a;
    int *c = a+1;
    printf("%ld", c-b);
 
    return 0;
}
What is the output of this program? (You may ignore compiler warnings)

#include <stdio.h>

int main()

{

int a[10][20][30] = {0};

int *b = a;

int *c = a+1;

printf("%ld", c-b);

return 0;

}

What is the output of this program? (You may ignore compiler warnings)

What is the output of the following program?

#include <stdio.h>
#include <stdlib.h>
int* fun();
 
int main()
{
    int *a = fun();
    printf("%d",*a);
 
    return 0;
}
int* fun()
{
    int *a =(int*) malloc(sizeof(int));
    *a = 10;
    return a;
}

#include <stdio.h>

#include <stdlib.h>

int* fun();

int main()

{

int *a = fun();

printf("%d",*a);

return 0;

}

int* fun()

{

int *a =(int*) malloc(sizeof(int));

*a = 10;

return a;

}

What is the output of the following program?

#include <stdio.h> int main() { int *a = fun(); printf("%d",a); return 0; } int fun() { int a = 10; return a; }

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#include <stdio.h>
int main()
{
    int *a = fun();
    printf("%d",a);

    return 0;
}
int fun()
{
    int a = 10;
    return a;
}
What is the output of the following program?

#include <stdio.h> #include <string.h> int main() { char string[] = "Hello"; printf("%zu %zu",sizeof(string),strlen(string)); return 0; }

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

int main()
{
    char string[] = "Hello";
    printf("%zu %zu",sizeof(string),strlen(string));

    return 0;
}
What is the output of the following program?

#include <stdio.h> int main() { float a = 0.5; if(a == 0.5) printf("Yes"); else printf("No"); return 0; }

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#include <stdio.h>
int main()
{
    float a = 0.5;
    if(a == 0.5)
        printf("Yes");
    else
        printf("No");

    return 0;
}
What is the output of the following program?

#include <stdio.h> #include <string.h> void foo(char *); int main() { char a[100] = {0}; printf("%zu %zu",sizeof(a),strlen(a)); return 0; }

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#include <stdio.h>
#include <string.h>
void foo(char *);

int main()
{
    char a[100] = {0};
    printf("%zu %zu",sizeof(a),strlen(a));

    return 0;
}
What is the output of the following program? (Assume input is 10)

#include <stdio.h> int main() { int a; printf("%d",scanf("%d",&a)); return 0; }

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#include <stdio.h>
int main()
{
    int a;
    printf("%d",scanf("%d",&a));

    return 0;
}

If the binary equivalent of 5.375 in normalised form is 01000000 10101100 00000000 00000000, what will be the output of the following program?

#include <stdio.h>
 
int main()
{
    float a=5.375;
    char *p;
    int i;
    p = (char*)&a;
    for(i=0; i<2; i++)
        printf("%x", (unsigned char)(p[i]^p[3-i]));
 
    return 0;
}

#include <stdio.h>

int main()

{

float a=5.375;

char *p;

int i;

p = (char*)&a;

for(i=0; i<2; i++)

printf("%x", (unsigned char)(p[i]^p[3-i]));

return 0;

}

What is the output of the following program?

#include <stdio.h> int main() { char str[] = {'a','b','c','\0'}; str[0] -= 32; printf("%s",str); return 0; }

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#include <stdio.h>
int main()
{
    char str[] = {'a','b','c','\0'};
    str[0] -= 32;
    printf("%s",str);

    return 0;
}

Questions from Datatypes

Consider an implementation where int is 4 bytes and long int is 8 bytes. Which of the following initializations are correct?

#include <stdio.h>
int main()
{
   long int a = 0x7fffffff * 0x7ffffff;
   long int b = 0x7ffffffff * 0x7ffffff;
   long int c = 0x7fffffff * 0x7fffffff;
   long int d = 0x7fffffff * 0x7fffffffl;
   printf("a = %ld, b = %ld, c = %ld, d = %ld\n", a, b, c, d);
   return 0;
}

#include <stdio.h>

int main()

{

long int a = 0x7fffffff * 0x7ffffff;

long int b = 0x7ffffffff * 0x7ffffff;

long int c = 0x7fffffff * 0x7fffffff;

long int d = 0x7fffffff * 0x7fffffffl;

printf("a = %ld, b = %ld, c = %ld, d = %ld\n", a, b, c, d);

return 0;

}

Consider an implementation where int is 4 bytes and long int is 8 bytes. What will be the output of the following code?

#include <stdio.h>
int main()
{
   int i = 0;
   size_t a = sizeof i, b = sizeof (long);
   printf("a = %zd, b = %zd\n", a, b); //If %zd is given the compiler will automatically give it the correct type whether short, long or normal. This is useful for special data types like size_t whose size is implementation specific
   return 0;
}

#include <stdio.h>

int main()

{

int i = 0;

size_t a = sizeof i, b = sizeof (long);

printf("a = %zd, b = %zd\n", a, b); //If %zd is given the compiler will automatically give it the correct type whether short, long or normal. This is useful for special data types like size_t whose size is implementation specific

return 0;

}

What will be the output of the following code?

#include <stdio.h> int main() { unsigned int a = 5; if(a > -1) printf("5 is > -1\n"); return 0; }

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#include <stdio.h>
int main()
{
   unsigned int a = 5;
   if(a > -1)
      printf("5 is > -1\n");
   return 0;
}
What will be printed by the following code?

#include <stdio.h> int main() { char buff[255] = "abc\ pee"; printf("%s", buff); return 0; }

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#include <stdio.h>

int main()
{
   char buff[255] = "abc\
pee";
   printf("%s", buff);
   return 0;
}
What will be printed by the following code?

#include <stdio.h> int main() { char buff[255] = "\0"; printf("%s", buff); return 0; }

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#include <stdio.h>

int main()
{
    char buff[255] = "\0";
    printf("%s", buff);
    return 0;
}

What will be the output of the following code? (Assume a 64 bit machine/compiler)

#include <stdio.h>
int main()
{
    char *p = "Hello World";
    char q[] = "Hello World";
    printf("%zd %zd", sizeof p, sizeof *p);
    printf("\n");
    printf("%zd %zd", sizeof q, sizeof *q);
    return 0;
}

#include <stdio.h>

int main()

{

char *p = "Hello World";

char q[] = "Hello World";

printf("%zd %zd", sizeof p, sizeof *p);

printf("\n");

printf("%zd %zd", sizeof q, sizeof *q);

return 0;

}

What will be the output of the following code?

#include <stdio.h>
int main()
{
   {
      char a = 5;
      int b = 5;
      if(a == b)          
         printf("char and int compared equal\n");    }
   {
      int a = 5;
      long int b = 5;
if(a == b)
         printf("int and long compared equal\n");
   }
   {
      float a = 5.0;
      double b = 5.0;
      if(a == b)
         printf("float and double compared equal\n");
   }
   {
      float a = 5.2;
      double b = 5.2;
      if(a == b)
         printf("float and double again compared equal\n");
   }
   {
      float a = 5.2;
      if(a == 5.2)
         printf("float compared equal with constant\n");
   }
   {
      double a = 5.2;
      if(a == 5.2)
         printf("double compared equal with constant\n");
   }
   return 0;
}

#include <stdio.h>

int main()

{

char a = 5;

int b = 5;

if(a == b)

printf("char and int compared equal\n"); }

{

int a = 5;

long int b = 5;

if(a == b)

printf("int and long compared equal\n");

}

{

float a = 5.0;

double b = 5.0;

if(a == b)

printf("float and double compared equal\n");

}

{

float a = 5.2;

double b = 5.2;

if(a == b)

printf("float and double again compared equal\n");

}

{

float a = 5.2;

if(a == 5.2)

printf("float compared equal with constant\n");

}

{

double a = 5.2;

if(a == 5.2)

printf("double compared equal with constant\n");

}

return 0;

}

Questions from Pointers

What will be the output of the following code?

#include <stdio.h> int main() { int a = 5; int* p = &a; printf("%d", ++*p); }

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#include <stdio.h>

int main()
{
  int a = 5;
  int* p = &a;
  printf("%d", ++*p);
}
What will be the output of the following code?

#include <stdio.h> int main() { char a[] = "Hello World"; char* p = &a; printf("%s", p+2 ); }

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#include <stdio.h>

int main()
{
  char a[] = "Hello World";
  char* p = &a;
  printf("%s", p+2 );
}
What will be the output of the following code?

#include <stdio.h> int main() { int a; int* p = &a; printf("%zu", sizeof( *(char*)p )); }

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#include <stdio.h>

int main()
{
  int a;
  int* p = &a;
  printf("%zu", sizeof( *(char*)p  ));
}

Is the following code legal?

#include <stdio.h>
 
int main()
{
  int a = 1;
  if((char*)  &a)
  {
    printf("My machine is little endian");
  }
  else
  {
     printf("My machine is big endian\n");
  }
}

#include <stdio.h>

int main()

{

int a = 1;

if((char*) &a)

{

printf("My machine is little endian");

}

else

{

printf("My machine is big endian\n");

}

What will be the output of the following code?

#include <stdio.h> int main() { int *a = (int*) 1; printf("%d", a); }

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#include <stdio.h>

int main()
{
int *a = (int*) 1;
printf("%d", a);
}
What will be the output of the following code?

#include <stdio.h> int main() { int a = 1, *p, **pp; p = &a; pp = p; printf("%d", **pp); }

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#include <stdio.h>

int main()
{
  int a = 1, *p, **pp;
  p = &a;
  pp = p;
  printf("%d", **pp);
}
What will be the output of the following code?

#include <stdio.h> int main() { int a = 1, *p, **pp; p = &a; pp = p; printf("%d", *pp); }

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#include <stdio.h>

int main()
{
  int a = 1, *p, **pp;
  p = &a;
  pp = p;
  printf("%d", *pp);
}

Assuming a little endian machine, what will be the output of the following program?

#include <stdio.h>
 
fun(int a)
{
  char *arr[] = {"0000", "0001","0010","0011","0100","0101","0110","0111","1000","1001","1010","1011","1100","1101","1110","1111"};
  unsigned char* p = (unsigned char*) &a ;
  p+=3;
  int i;
  for(i = 0; i < sizeof a; i++) { int d = (*p)>>4; 
    printf("%s", arr[d]);
    d = (*p) & 0xf;
    printf("%s ", arr[d]);
    p--;
  }
}
 
int main()
{
 int a;
 scanf("%d", &a);
 fun(a);
}

#include <stdio.h>

fun(int a)

{

char *arr[] = {"0000", "0001","0010","0011","0100","0101","0110","0111","1000","1001","1010","1011","1100","1101","1110","1111"};

unsigned char* p = (unsigned char*) &a ;

p+=3;

int i;

for(i = 0; i < sizeof a; i++) { int d = (*p)>>4;

printf("%s", arr[d]);

d = (*p) & 0xf;

printf("%s ", arr[d]);

p--;

}

int main()

{

int a;

scanf("%d", &a);

fun(a);

}

Some codes

What is the following function doing?

int foo(int n) { int sum = 0; while(n > 0) { n = n & n-1; sum++; } return sum; }

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int foo(int n)
{
    int sum = 0;
    while(n > 0)
    {
        n = n & n-1;
        sum++;
    }
    return sum;
}

What is the following function doing?

int foo(int a, int b)
{
    int c = a, d = b;
    while(a != b)
    {
        if(a &lt; b)
            a = a+c;
        else
            b = b+d;
    }
    return a;
}

int foo(int a, int b)

{

int c = a, d = b;

while(a != b)

{

if(a < b)

a = a+c;

else

b = b+d;

}

return a;

}

What is the following function doing?

int foo( int a, int b) { int c = a-b; c = c&(0x80000000); return (!c)*a +(!!c)*b; }

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int foo( int a, int b)
{
    int c = a-b;
    c = c&(0x80000000);
    return (!c)*a +(!!c)*b;
}

What is the following function doing?

unsigned fun(unsigned a, unsigned b)
{
    int i;
    unsigned  j = 0;
    for(i = 0; i &lt; 32; i++)
    {
        j &lt;&lt;= 1;
        j += !!(a &amp; 0x80000000);
        a &lt;&lt;= 1; if(j &gt;=b)
        {
            j -= b;
            a++;
        }
    }
    return a;
}

unsigned fun(unsigned a, unsigned b)

{

int i;

unsigned j = 0;

for(i = 0; i < 32; i++)

{

j <<= 1;

j += !!(a & 0x80000000);

a <<= 1; if(j >=b)

{

j -= b;

a++;

}

return a;

}

What is the following function doing?

unsigned fun(unsigned int a)
{
    unsigned int i, x = 0, y = 0, z = 0;
    for(i = 0; i &lt; 16; i++)
    {
       	y &lt;&lt;= 2;
       	y += !!(a &amp; 0x80000000) &lt;&lt; 1;
       	y += !!(a &amp; 0x40000000);
       	a &lt;&lt;= 2;
       	x = x + (x&amp;1);
       	x &lt;&lt;= 1;
       	z &lt;&lt;= 1;
       	if(x + 1 &lt;= y)
       	{
            x++;
            z++;
	    y-=x;
        }
    }
    return z;
}

unsigned fun(unsigned int a)

{

unsigned int i, x = 0, y = 0, z = 0;

for(i = 0; i < 16; i++)

{

y <<= 2;

y += !!(a & 0x80000000) << 1;

y += !!(a & 0x40000000);

a <<= 2;

x = x + (x&1);

x <<= 1;

z <<= 1;

if(x + 1 <= y)

{

x++;

z++;

y-=x;

}

return z;

}

Write the code to dynamically allocate a 2-D array of size m x n.
Declare a pointer to a function accepting an integer and returning void.
Write the condition so that the below code outputs Hello World.

#include <stdio.h> int main() { if() { printf("Hello "); } else { printf("World\n"); } return 0; }

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#include <stdio.h>
int main()
{
    if()
    {
printf("Hello ");
    }
    else
    {
printf("World\n");
    }

    return 0;
}
Write a one line code to check if a number is a power of 2.
Write a one line code to invert the last four bits of an integer.

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