Create 298. Binary Tree Longest Consecutive Sequence.cpp

Author: fengvyi

C++/298. Binary Tree Longest Consecutive Sequence.cpp

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+// DFS
+class Solution {
+public:
+    int longestConsecutive(TreeNode* root) {
+        int maxlen = 0;
+        DFS(NULL, root, 1, maxlen);
+        return maxlen;
+    }
+    
+    void DFS(TreeNode* from, TreeNode* cur, int len, int& maxlen){
+        if(!cur) return;
+        len = (from && cur->val == from->val + 1) ? len + 1 : 1;
+        maxlen = max(maxlen, len);
+        DFS(cur, cur->left, len, maxlen);
+        DFS(cur, cur->right, len, maxlen);
+    }
+};
+
+// BFS
+class Solution {
+public:
+    int longestConsecutive(TreeNode* root) {
+        if(!root) return 0;
+        deque<pair<TreeNode*, int>>q;
+        q.push_back({root, 1});
+        int maxlen = 0;
+        while(!q.empty()){
+            auto p = q.front();
+            q.pop_front();
+            if(p.first->left) q.push_back({p.first->left, (p.first->left->val == p.first->val + 1) ? p.second + 1 : 1});
+            if(p.first->right) q.push_back({p.first->right, (p.first->right->val == p.first->val + 1) ? p.second + 1 : 1});
+            maxlen = max(maxlen, p.second);
+        }
+        return maxlen;
+    }
+};