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Remove Duplicates from Sorted List in C++
Suppose we have a sorted linked list; we have to delete all duplicates such that each element appears only once.
So, if the input is like [1,1,2,3,3,3,4,5,5], then the output will be [1,2,3,4,5]
To solve this, we will follow these steps −
dummy := make a new node with value -inf
next of dummy := head
curr = dummy
while curr is non-zero, do −
next = next of curr
while (next is not null and val of next is same as val of curr), do −
next := next of next
next of curr := next
curr := next
return next of dummy
Example
Let us see the following implementation to get a better understanding −
#include <bits/stdc++.h>
using namespace std;
class ListNode{
public:
int val;
ListNode *next;
ListNode(int data){
val = data;
next = NULL;
}
};
ListNode *make_list(vector<int> v){
ListNode *head = new ListNode(v[0]);
for(int i = 1; i<v.size(); i++){
ListNode *ptr = head;
while(ptr->next != NULL){
ptr = ptr->next;
}
ptr->next = new ListNode(v[i]);
}
return head;
}
void print_list(ListNode *head){
ListNode *ptr = head;
cout << "[";
while(ptr){
cout << ptr->val << ", ";
ptr = ptr->next;
}
cout << "]" << endl;
}
class Solution {
public:
ListNode* deleteDuplicates(ListNode* head) {
ListNode*dummy = new ListNode(INT_MIN);
dummy->next = head;
ListNode * curr = dummy;
while(curr){
ListNode * next = curr->next;
while(next && next->val==curr->val)
next = next->next;
curr->next = next;
curr=next;
}
return dummy->next;
}
};
main(){
Solution ob;
vector<int> v = {1,1,2,3,3,3,4,5,5};
ListNode *head = make_list(v);
print_list(ob.deleteDuplicates(head));
}Input
{1,1,2,3,3,3,4,5,5}Output
[1, 2, 3, 4, 5, ]
Updated on: 10-Jun-2020
1K+ Views
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