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  1. /*Adobe Elitmus Written Test on 27-10-2013  @Bangalore - Algo/DS questions
  2.  *Question 1
  3.  */
  4.  
  5. /* Reverse every alterante K elements of a list 
  6.  * It is to be noted that Nodes have to reversed and not the values
  7.  * e.g. if k=3 and list is
  8.  * Input 1->2->3->4->5->6->7->8->9->NULL
  9.  * Output 3->2->1->4->5->6->9->8->7->NULL
  10.  * 
  11. */
  12.  
  13. #include<stdio.h>
  14. #include<stdlib.h>
  15.  
  16. typedef struct SLL{
  17. 	int element;
  18. 	struct SLL *next;
  19. }Node;
  20.  
  21. Node *start=NULL;
  22.  
  23. void InsertNode(Node *start, int item)
  24. {
  25. 	Node *tmp=start;
  26.  
  27. 	if(tmp == NULL)
  28. 	{
  29. 		printf("Error : Start pointer is NUll\n");
  30. 		return;
  31. 	}
  32.  
  33. 	//construct a node with item element
  34. 	Node *node=malloc(sizeof(Node));
  35. 	node->next=NULL;
  36. 	node->element=item;
  37.  
  38. 	while(tmp->next !=NULL) tmp=tmp->next;
  39.  
  40. 	tmp->next=node; //node inerted at end
  41. }
  42.  
  43. void PrintListElements(Node *start)
  44. {
  45. 	Node *tmp=start;
  46.  
  47. 	while(tmp != NULL)
  48. 	{
  49. 		printf("%d->",tmp->element);
  50. 		tmp=tmp->next;
  51. 	}
  52. 		printf("NULL\n");
  53. }
  54.  
  55. void ReverseAlternateKElements(Node *start, int K, Node **startPointer)
  56. {
  57. 	int i,j,count;
  58. 	Node *current=start;
  59. 	Node *prev=NULL,*prev2=NULL;
  60. 	Node *save=NULL;
  61. 	Node *next=NULL;
  62. 	Node *tmp=NULL;
  63.  
  64. 	for(i=0;;)
  65. 	{
  66. 		if(current == NULL) break;
  67. 		if(i%K==0)
  68. 		{
  69. 			count=0;
  70. 			save=current;
  71. 			//printf("current=%d\n",current->element);
  72. 			for(j=0;j<K;)
  73. 			{
  74. 				if(current == NULL) break;
  75. 				next=current->next;	
  76. 				current->next=prev;
  77. 				prev=current;
  78. 				current=next;
  79. 				j++;
  80. 				++count;
  81. 			}
  82. 			if(i<K) 
  83. 			{
  84. 				*startPointer=prev;
  85. 				tmp=prev;
  86. 			}
  87. 			save->next=current; // for last node of the series to point to next current;
  88.  
  89. 			if(prev2 != NULL)
  90. 				prev2->next=prev;
  91. 			if(current == NULL) break;
  92. 			//PrintListElements(tmp);
  93. 			i=i+count+1;
  94.  
  95. 		}
  96. 		else
  97. 		{
  98.  
  99. 			current = current->next;
  100. 			if(current == NULL) break;
  101. 			i++;
  102. 			if(i%K==0) 
  103. 			{
  104. 				prev=current;
  105. 				prev2=current;
  106. 				current=current->next;
  107. 			}
  108. 		}
  109. 	}
  110.  
  111. 	printf("----Reversal Done!!! :)\n");
  112. 	//PrintListElements(tmp);
  113.  
  114. }
  115.  
  116.  
  117.  
  118. int main()
  119. {
  120. 	int K=4; //Input
  121. 	start=malloc(sizeof(Node));
  122.  
  123.  
  124. 	start->next=NULL;
  125. 	start->element=1; // Inputs
  126. 	InsertNode(start,2); //Inputs .....
  127. 	InsertNode(start,3);
  128. 	InsertNode(start,4);
  129. 	InsertNode(start,5);
  130. 	InsertNode(start,6);
  131. 	InsertNode(start,7);
  132. 	InsertNode(start,8);
  133. 	InsertNode(start,9);
  134. 	InsertNode(start,10);
  135. 	InsertNode(start,11);
  136. 	InsertNode(start,12);
  137. 	InsertNode(start,13);
  138. 	InsertNode(start,14);
  139.  
  140. 	printf("Element Before Reversal:\n");
  141. 	PrintListElements(start);
  142.  
  143. 	ReverseAlternateKElements(start, K, &start);
  144.  
  145.  
  146. 	printf("Element After Reversal:\n");
  147. 	PrintListElements(start);
  148.  
  149. 	return 0;
  150. }	
  151.  
Success #stdin #stdout 0s 2424KB
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Standard input is empty
stdout
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Element Before Reversal:
1->2->3->4->5->6->7->8->9->10->11->12->13->14->NULL
----Reversal Done!!! :)
Element After Reversal:
4->3->2->1->5->6->7->8->12->11->10->9->13->14->NULL
https://ideone.com/QWnJAC
language:
C (gcc 8.3)
created:
10 years ago
visibility:
public

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