Add

Author: yanglr

cpp-leetcode/leetcode23-merge-k-sorted-lists.cpp

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+#include <iostream>
+#include <vector>
+#include <queue>
+#include <algorithm>
+using namespace std;
+
+/**
+ * Definition for singly-linked list.
+ */
+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) {}
+};
+
+class Solution {
+public:
+    ListNode *mergeKLists(vector<ListNode *> &lists)
+    {
+        if (lists.size() == 0)
+            return NULL;
+
+        ListNode *res;
+        auto cmp = [](ListNode *n1, ListNode *n2)
+        {
+            return n1->val > n2->val;
+        };
+
+        /* 使用node的val构造一个小顶堆 */
+        priority_queue<ListNode *, vector<ListNode *>, decltype(cmp)> nodes(cmp);
+        for (auto list : lists)
+        {
+            if (list != NULL)
+            {
+                nodes.push(list);
+            }
+        }
+
+        ListNode *fakeHead = new ListNode(-1);  /* 创建虚拟头结点 */
+        ListNode *cur = fakeHead;
+        while (!nodes.empty()) 
+        {
+            cur->next = nodes.top();  /* 取出最小值对应的结点指针，挂接在游标指针上 */
+            cur = cur->next;
+            nodes.pop();
+
+            if (cur->next != NULL)  /* 只要挂接点后面还有结点，则将其压入栈，继续从中拿出最大值，循环往复 */
+            {
+                nodes.push(cur->next);
+            }
+        }
+
+        return fakeHead->next;
+    }
+};
+
+// Test
+int main()
+{   
+    Solution sol;
+    // l1 = {1,2,4}, l2 = {1,3,4}
+    ListNode *l1 = new ListNode(1);
+    l1 -> next = new ListNode(2);
+    l1 -> next -> next = new ListNode(4);
+    ListNode *l2 = new ListNode(1);
+    l1 -> next = new ListNode(3);
+    l1 -> next -> next = new ListNode(4);
+    vector<ListNode*> vec;
+    vec.push_back(l1);
+    vec.push_back(l2);
+    ListNode* res = sol.mergeKLists(vec);
+
+    ListNode *p = res;
+    while (p != NULL)
+    {
+        cout << p->val << endl;
+        p = p->next;
+    }    
+
+    return 0;
+}