forked from prateekshyap/DSA
-
Notifications
You must be signed in to change notification settings - Fork 0
/
GFG_RemoveLoopLL.cpp
175 lines (137 loc) · 3.14 KB
/
GFG_RemoveLoopLL.cpp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
/*
* https://practice.geeksforgeeks.org/problems/remove-loop-in-linked-list/1
* Remove loop in Linked List
*/
// { Driver Code Starts
// driver code
#include <iostream>
using namespace std;
struct Node
{
int data;
Node* next;
Node(int val)
{
data = val;
next = NULL;
}
};
void loopHere(Node* head, Node* tail, int position)
{
if(position==0) return;
Node* walk = head;
for(int i=1; i<position; i++)
walk = walk->next;
tail->next = walk;
}
bool isLoop(Node* head)
{
if(!head) return false;
Node* fast = head->next;
Node* slow = head;
while( fast != slow)
{
if( !fast || !fast->next ) return false;
fast=fast->next->next;
slow=slow->next;
}
return true;
}
int length(Node* head)
{
int ret = 0;
while(head)
{
ret++;
head = head->next;
}
return ret;
}
// } Driver Code Ends
/*
structure of linked list node:
struct Node
{
int data;
Node* next;
Node(int val)
{
data = val;
next = NULL;
}
};
*/
class Solution
{
public:
//Function to remove a loop in the linked list.
void removeLoop(Node* head)
{
// code here
// just remove the loop without losing any nodes
// if empty LL or one node or two node without cycle.
if(!head || !head->next || !head->next->next) return ;
Node* slow = head, *fast = head;
Node* deln = head;
slow = slow->next;
fast = fast->next->next;
deln = deln->next; // just behind fast node
// if(head->next == head)
// {
// head->next == nullptr;
// return;
// }
while(slow && fast && fast->next)
{
if(slow == fast) break;
slow = slow->next;
deln = fast;
deln = deln->next ;// just behind fast node
fast = fast->next->next;
}
// if no loop exists
if(slow != fast) return; //|| !fast || !fast->next
// if loop exists
slow = head; // start from head node
// if(slow == fast) // loop at begining of head node
while(slow != fast)
{
slow = slow->next;
deln = fast;
fast = fast->next;
}
deln->next = nullptr;
return;
}//end
};
// { Driver Code Starts.
int main()
{
int t;
cin>>t;
while(t--)
{
int n, num;
cin>>n;
Node *head, *tail;
cin>> num;
head = tail = new Node(num);
for(int i=0 ; i<n-1 ; i++)
{
cin>> num;
tail->next = new Node(num);
tail = tail->next;
}
int pos;
cin>> pos;
loopHere(head,tail,pos);
Solution ob;
ob.removeLoop(head);
if( isLoop(head) || length(head)!=n )
cout<<"0\n";
else
cout<<"1\n";
}
return 0;
}
// } Driver Code Ends