0543_Diameter_of_Binary_Tree.cpp

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */

#pragma GCC optimize("Ofast","inline","ffast-math","unroll-loops","no-stack-protector")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native","f16c")
class Solution {
public:
    int solve(TreeNode* root, int& res){
        if(root==NULL){
            return 0;
        }
        int l = solve(root->left, res);
        int r= solve(root->right, res);

        res= max(res, (l+r));
        return max(l,r)+1;
    }
    int diameterOfBinaryTree(TreeNode* root) {
        if(root==NULL){
            return 0;
        }
        int res = INT_MIN;
        solve(root, res);
        return res;
    }
};