leetcode

Daily Problem

1 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/ Problems/0023.cpp b/ Problems/0023.cpp

@@ -1,3 +1,4 @@

// Naive solution, barely passed

class Solution { public: ListNode *mergeKLists(vector<ListNode *> &lists) {

@@ -20,3 +21,28 @@ public: return dummy->next; } };

// Proper solution

class Solution {

typedef pair<int, int> pii;

public:

ListNode *mergeKLists(vector<ListNode *> &lists) {

ListNode *dummy, *tmp;

tmp = dummy = new ListNode;

auto cmp = [](const pii &a, const pii &b) { return a.first > b.first; };

priority_queue<pii, vector<pii>, decltype(cmp)> pq(cmp);

for (int i = 0; i < lists.size(); i++)

if (lists[i]) pq.push({lists[i]->val, i});

while (!pq.empty()) {

int index = pq.top().second;

pq.pop();

ListNode *t = lists[index];

lists[index] = lists[index]->next;

if (lists[index]) pq.push({lists[index]->val, index});

tmp = tmp->next = t;

}

return dummy->next;

}

};