Remove Duplicates from Sorted List II Problem
Description
LeetCode Problem 82.
Given the head of a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list. Return the linked list sorted as well.
Example 1:
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Input: head = [1,2,3,3,4,4,5]
Output: [1,2,5]
Example 2:
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Input: head = [1,1,1,2,3]
Output: [2,3]
Constraints:
- The number of nodes in the list is in the range [0, 300].
- -100 <= Node.val <= 100
- The list is guaranteed to be sorted in ascending order.
Sample C++ Code
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class Solution {
public:
ListNode* deleteDuplicates(ListNode* head) {
if ((head == NULL) || (head->next == NULL))
return head;
ListNode* curr = head;
map<int, int> cnt;
while (curr != NULL) {
if (cnt.find(curr->val) != cnt.end()) {
cnt[curr->val] ++;
} else {
cnt[curr->val] = 1;
}
curr = curr->next;
}
int first_num;
bool is_empty = true;
for (map<int,int>::iterator mit = cnt.begin(); mit != cnt.end();
mit ++) {
if (mit->second == 1) {
first_num = mit->first;
is_empty = false;
break;
}
}
if (is_empty)
return NULL;
curr = head;
ListNode* new_head;
ListNode* prev;
while (curr != NULL) {
if (curr->val == first_num) {
new_head = curr;
break;
}
curr = curr->next;
}
prev = new_head;
curr = new_head->next;
while (curr != NULL) {
if (cnt[curr->val] == 1) {
prev->next = curr;
prev = prev->next;
}
curr = curr->next;
}
prev->next = NULL;
return new_head;
}
};