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insertion-sort-list.cpp
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insertion-sort-list.cpp
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// Time: O(n^2)
// Space: O(1)
/**
* Definition of ListNode
* class ListNode {
* public:
* int val;
* ListNode *next;
* ListNode(int val) {
* this->val = val;
* this->next = NULL;
* }
* }
*/
class Solution {
public:
/**
* @param head: The first node of linked list.
* @return: The head of linked list.
*/
ListNode *insertionSortList(ListNode *head) {
ListNode dummy(INT_MIN);
ListNode *cur = head;
ListNode *prev = nullptr;
ListNode *pos = nullptr;
while (cur) {
pos = findInsertPos(&dummy, cur->val);
ListNode *tmp = cur->next;
cur->next = pos->next;
pos->next = cur;
cur = tmp;
}
return dummy.next;
}
ListNode* findInsertPos(ListNode *head, int x) {
ListNode *pre = nullptr;
for (ListNode *cur = head; cur && cur->val <= x;
pre = cur, cur = cur->next);
return pre;
}
};