题目：
用哈希表来查找要删除的元素，将时间复杂度降低到 O(n)
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| #include <climits>
struct ListNode {
int val;
ListNode *next;
ListNode()
: val(0)
, next(nullptr)
{
}
ListNode(int x)
: val(x)
, next(nullptr)
{
}
ListNode(int x, ListNode *next)
: val(x)
, next(next)
{
}
};
#include <vector>
#include <unordered_set>
using std::vector;
using std::unordered_set;
class Solution {
public:
ListNode *modifiedList(vector<int> &nums, ListNode *head)
{
int i, n;
ListNode dummy;
dummy.next = head;
dummy.val = INT_MAX;
ListNode *p = &dummy;
n = nums.size();
unordered_set<int> uset;
ListNode *tmp;
for (i = 0; i < n; i++) {
uset.insert(nums[i]);
}
while (p->next) {
if (uset.count(p->next->val) != 0) {
tmp = p->next;
p->next = tmp->next;
delete tmp;
}else{
p = p->next;
}
}
return dummy.next;
}
};
#include <iostream>
using std::cout;
using std::endl;
int main() {
vector<int> nums = {1, 2, 3};
ListNode *head = new ListNode(1, new ListNode(2, new ListNode(3, new ListNode(4, new ListNode(5)))));
Solution s;
ListNode *res = s.modifiedList(nums, head);
while (res) {
cout << res->val;
if (res->next) cout << " -> ";
res = res->next;
}
cout << endl;
return 0;
}
|
