Create findMedianFromDataStream.cpp

Linked list approach Leetcode Hard Problem 295. Find Median from Data Stream

findMedianFromDataStream.cpp

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+class MedianFinder {
+    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) {}
+    };  
+
+private:
+    double getMedian(ListNode* head) {
+        if(head->next == NULL){
+            return head->val;
+        }
+        else {
+            ListNode * fast = head->next;
+            ListNode * slow = head;
+            while(fast != NULL){
+                fast = fast->next;
+                if(fast==NULL){
+                    return (double)(slow->val + slow->next->val) / (double)2;
+                }
+                fast = fast->next;
+                slow = slow->next;
+            }
+
+            return slow->val;
+        }
+    }
+
+public:
+    ListNode* head = NULL;
+    ListNode* tail = NULL;
+    MedianFinder() {
+        // ListNode* head = NULL;
+        // ListNode* tail = NULL;
+    }
+
+    void addNum(int num) {      
+
+        ListNode* node = new ListNode(num);
+        //empty list
+        if(head == NULL) {
+            head = node;
+            tail = node;
+            return;
+        }
+
+        //one node
+        else if(head->next == NULL){
+            if(head->val <= num){
+                head->next = node;
+                tail = node;
+            }else{
+                node->next = head;
+                head = node;
+                tail = node->next;
+            }
+        }
+
+        //multiple node
+        else if(tail->val <= num){
+            tail->next = node;
+            tail = node;
+        }
+
+        else{
+            if(tail->val > num && head->val >= num){
+                node->next = head;
+                head = node;
+            }else{
+                ListNode * curr = head->next;
+                ListNode * prev = head;
+
+                while(curr!=NULL){
+                    if(curr->val >= num){
+                        prev->next = node;
+                        node->next = curr;
+                        break;
+                    }
+                    prev = curr;
+                    curr = curr->next;
+                }
+            }
+        }
+    }
+
+    double findMedian() {
+        return getMedian(head);
+    }
+};
+
+/**
+ * Your MedianFinder object will be instantiated and called as such:
+ * MedianFinder* obj = new MedianFinder();
+ * obj->addNum(num);
+ * double param_2 = obj->findMedian();
+ */