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  • [leetcode-687-Longest Univalue Path]

    Given a binary tree, find the length of the longest path where each node in the path has the same value. This path may or may not pass through the root.

    Note: The length of path between two nodes is represented by the number of edges between them.

    Example 1:

    Input:

                  5
                 / 
                4   5
               /    
              1   1   5
    

    Output:

    2
    

    Example 2:

    Input:

                  1
                 / 
                4   5
               /    
              4   4   5
    

    Output:

    2
    

    Note: The given binary tree has not more than 10000 nodes. The height of the tree is not more than 1000.

    思路:

    求与当前结点相同的路径长度的时候,类似于先序遍历。

    
    
     int longPath(TreeNode* root,int pre)//与当前结点相同的最长路径长度
     {
       if(root == NULL ||  root->val != pre) return 0;
       int left = longPath(root->left,root->val);
       int right = longPath(root->right,root->val);
       return 1+max(left,right);      
    }
     int longestUnivaluePath(TreeNode* root)
     {
        int ret = 0;
        if(root == NULL) return 0;
        int left = longestUnivaluePath(root ->left);
        int right = longestUnivaluePath(root->right);
        ret = max(max(left,right),longPath(root->left,root->val)+longPath(root->right,root->val));
        return ret;
     }
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  • 原文地址:https://www.cnblogs.com/hellowooorld/p/7636155.html
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