CareerCup

Yes, but this is not in place.

#define SIZE 7
int tab[SIZE]={ 1,0,2,0,0,3,4};

void f(void)
{
  int swapped, i, j, temp;
  swapped=1;
  i=0;
  j=0;
  while(swapped)
  {
    swapped=0;
    while((i<SIZE)&&(j<SIZE))
    {
      while((tab[i]==0)&&(i<SIZE))
        i++;
      while((tab[j]!=0)&&(j<SIZE))
        j++;
      if((i<SIZE)&&(j<SIZE))
      {
        temp = tab[i];
        tab[i] = tab[j];
        tab[j] = temp;
        swapped=1;
      }
    }  
  }
}

void main()
{
  int i;
  f();
  for(i=0; i<SIZE ; i++)
  {
    printf("\n %d: %d", i, tab[i]);
  }
  exit(000);
}

I replied above for the "inefficient". Let me reply for the "incorrect". I made a small change with "while" instead of "if" and tested it OK.

#include <stdio.h>

int keyval[] = { 1000, 900, 500, 400, 100,90, 50, 40, 10, 9, 5, 4, 1 };
char keystr[13][3] = { "M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I" };
char str[] = "XXIV";

void decode()
{
  char *ptr=str;
  int i, l;
  int val=0;
  for(i=0; i<13 ; i++)
  {
    l=strlen(keystr[i]);
    while(!strncmp(ptr,keystr[i],l))
    {
      val+=keyval[i];
      ptr+=l;
    }
  }
  printf("\n val: %d", val);
}

void main()
{
  int i;
  decode();
  exit(000);
}

This is one pass scan Sir!
if the strlen bothers you, replace 'l' with ls[i] with ls defined as follow: int ls[]={ 1, 2, 1, 2, etc...

int keyval[] = { 1000, 900, 500, 400, 100,90, 50, 40, 10, 9, 5, 4, 1 };
char keystr[13][] = { "M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I" };
int i;
char str[] = "XXIV";
char *ptr=str;
int val=0;
for(i=0; i<13 ; i++)
{
  l=strlen(keystr[i]);
  if(!strncmp(ptr,keystr[i],l))
  {
    val+=keyval[i];
    ptr+=l;
  }
}
printf("\n val: %d", val);

#define SIZE 3
int tab[SIZE]={4, 10, 15};
int score=80;

int f(s)
{
  printf(" %d", s);
  if(s<0) 
  {
    printf(" nope\n");
    return(0);
  }
  else
  if(!s)
  {
    printf(" found\n");
    return(1);
  }
  else
  {
    return(f(s-tab[0]) || f(s-tab[1]) || f(s-tab[2]));
  }
}

The lines ending with found is the results

#define SIZE 3
int tab[SIZE];
int pages[]={1,3};

for(i=0; i<SIZE ; i++)
{
  tab[i]=0;
}

for(i=0; i<SIZE-1 ; i++)
{
  tab[pages[i]]=1;
}

for(i=0; i<SIZE ; i++)
{
  if(!tab[i]) printf("\n i: %d is missing", i);
}

Use bubble sort because it is simple and it use a constant space + 1 cell for the swap.
Order from high to low.

#define SIZE 3
int tab[SIZE];
int swapped=1;
while(swapped)
{
  swapped=0;
  for(i=0; i<SIZE-1 ; i++)
  {
    if(tab[i]<tab[i+1])
    {
      temp = tab[i];
      tab[i] = tab[i+1];
      tab[i+1] = temp;
      swapped=1;
    }
  }
}
for(i=0; i<SIZE ; i++)
{
  printf("%d", tab[i]);
}

typedef struct TreeNode 
{
  int element;
  struct TreeNode *left, *right;
} TreeNode;

TreeNode *displayTree(TreeNode *node)
{
  //display the full tree
  if(node==NULL)
  {
    return;
  }
  displayTree(node->left);
  printf("| %d ", node->element); 
  displayTree(node->right);
}

oops typo >=
for(i=strlen(str)-1; i>=0; i--)

char str[] = "Hello World";
char str2[] = "";
int i;
for(i=strlen(str)-1; i<=0; i--)
{
  if(str[i]==' ')
  {
    strcat(str2,str+i+1);
    strcat(str2," ");
    str[i]=0;  // cut
  }
}
// first that becomes last
strcat(str2,str);
printf("\n str: %s", str2);

char str1[] = "abcrfghwetf";
char str2[] = "abrfghwwetxyab";
int max, i, j, l1, l2, cnt, sovi, sovj;
max=0;
l1=strlen(str1);
l2=strlen(str2);

for(i=0; i<l1 ; i++)
{
  cnt=0;
  for(j=i; j<l2 ; j++)
  {
    if((str1[i]==str2[j]))
    {
      cnt++;
      i++;
      j++
    }
    else
      break;
  }  
  if(cnt>max)
    {
    max=cnt;
    sovi=i;
    sovj=j;
    }
}
printf("\n str: %s", str1+i-cnt);

This returns the 4th largest number. replace 4 by k and 3 with k-1 to answer the question.

char str[] = "Hello WorldHe";
int i, j, l, cnt;
l=strlen(str);
for(i=0; i<l ; i++)
{
  cnt=0;
  for(j=i+1; j< ; j++)
  {
    if(str[j]==str[i])
      cnt++;
  }  
  if(!cnt)
  {
    printf("\n i: %d", i);
    break;
  }
}