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  1. import java.util.*;
  2.  
  3. class ListNode{ // structure of one SLL Node
  4. 	int val;
  5. 	ListNode next;
  6. 	// Constructor - method - create/instantiate objects - alloc memory and init all members
  7. 	public ListNode(int v){
  8. 		val = v; next = null;
  9. 	}
  10. }
  11.  
  12.  
  13.  
  14. class Main{
  15. 	static Scanner sc = new Scanner(System.in);
  16. 	public static void main(String[] args){
  17. 		Solution sol = new Solution();
  18. 		ListNode h = null; // head of LL (empty)
  19. 		int n = sc.nextInt();
  20. 		while(n-->0){
  21. 			int x = sc.nextInt();
  22. 			h = sol.insertAtBegin(h, x);
  23. 		}
  24. 		sol.printLL(h);
  25. 		System.out.println();
  26. 		int findPrev = sc.nextInt();
  27. 		ListNode ans = sol.findPrevOf(h, findPrev);
  28. 		if(ans == null)
  29. 			System.out.println("null");
  30. 		else
  31. 			System.out.println(ans.val);
  32. 	}
  33. }
  34.  
  35. class Solution {
  36. 	// params - where to insert, what to insert
  37. 	// returns - new head after insertion
  38. 	ListNode insertAtBegin(ListNode h, int x){
  39. 		ListNode nn = new ListNode(x); // new node
  40. 		nn.next = h;
  41. 		return nn; // new head
  42. 	}
  43.  
  44. 	void printLL(ListNode h){
  45. 		ListNode t = h;
  46. 		while(t != null){
  47. 			System.out.print(t.val + " ");
  48. 			t = t.next;
  49. 		}
  50. 	}	
  51.  
  52. 	int countX(ListNode h, int x){
  53. 		ListNode t = h;
  54. 		int c = 0;
  55. 		while(t != null){
  56. 			if(t.val == x)
  57. 				c++;
  58. 			t = t.next;
  59. 		}
  60. 		return c;		
  61. 	}
  62. 	// sum of elems
  63.  
  64. 	// max/min val
  65.  
  66. 	ListNode find(ListNode h, int x){
  67. 		ListNode t = h;
  68. 		while(t != null){
  69. 			if(t.val == x)
  70. 				return t;
  71. 			t = t.next;
  72. 		}
  73. 		return null;
  74. 	}
  75.  
  76. 	ListNode findPrevOf(ListNode h, int x){
  77. 		ListNode p = null, t = h; // prev & temp
  78. 		while(t != null){
  79. 			if(t.val == x)
  80. 				return p;
  81. 			p = t;
  82. 			t = t.next;
  83. 		}
  84. 		return null;
  85. 	}
  86. }
  87.  
  88.  
  89.  
  90.  
  91.  
  92.  
Success #stdin #stdout 0.16s 41768KB
comments (?)
stdin 
5
5 4 3 2 1
1
stdout 
1 2 3 4 5 
null
https://ideone.com/33JMFG
language:
Java (HotSpot 12)
created:
245 days ago
visibility:
secret

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