[004] last_k_node

[Description]Find the k-th node from the last node of single linked list.

E.g. Linked-list: 1-2-3-4-5-6-7-8-9

The last 4th node is: 6

[Thought]Using two node point which are separated by K-2 nodes and moving them together. O (n)

[Implementation]C code:

1 # include <stdio. h> 2 # include <stdlib. h> 3 4 // construct single linked list. 5 typedef struct node 6 {7 int data; 8 struct node * next; 9} linklist, * pLL; 10 11 // create a linked list from array.12 pLL createLL (int seq [], int size) 13 {14 int I; 15 pLL phead, pnode; 16 17 if (size> = 1) 18 {19 phead = pnode = (pLL) malloc (sizeof (linklist); 20 pnode-> next = NULL; 21 pnode-> data = seq [0]; 22} 23 else24 {25 printf ("ERR OR: No element in array! "); 26 return NULL; 27} 28 29 for (I = 1; I <size; I ++) 30 {31 32 pnode-> next = (pLL) malloc (sizeof (linklist); 33 pnode = pnode-> next; 34 pnode-> next = NULL; 35 pnode-> data = seq [I]; 36} 37 return phead; 38} 39 40 // find the Kth node from the last one.41 int lastKnode (pLL pll, int k) 42 {43 linklist * m, * n; 44 m = pll; 45 int I; 46 47 for (I = 1; I <k; I ++) 48 {49 if (m! = NULL) 50 {51 m = m-> next; 52} 53 else54 {55 printf ("ERROR: The length of linklist is less than k! "); 56 return-1; 57} 58} 59 n = pll; 60 61 while (m-> next! = NULL) 62 {63 m = m-> next; 64 n = n-> next; 65} 66 return n-> data; 67} 68 69 main () 70 {71 int seq [] = {1, 2, 4, 5, 6, 7, 8, 9}; 72 int size; 73 pLL pll; 74 pll = NULL; 75 size = sizeof (seq) /sizeof (seq [0]); 76 pll = createLL (seq, size); 77 78 int k = 3; 79 printf ("The % dth node from the last is: % d \ n ", k, lastKnode (pll, k); 80}

 

[004] last_k_node