DFS(深度搜索) & BFS(广度搜索)

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};*/
class Solution {
public:
    // 自底向上搜索
    int DFS1(TreeNode* root) {
      if (root == nullptr) {
        return 0;
      }
      int left = DFS1(root->left);
      int right = DFS1(root->right);

      return left > right ? left + 1 : right + 1;
  }

 // 自顶向下搜索
int depthRes = 0;
void DFS2(TreeNode* root,int depth) {
    if (root == nullptr) {
        return;
    }
    depth = depth + 1;
    if(depth > depthRes) {
        depthRes = depth;
    }
    DFS2(root->left, depth);
    DFS2(root->right, depth);
}


};

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};*/
class Solution {
public:
// 广度搜索
int BFS(TreeNode* root)
{
    if (root == nullptr) {
        return 0;
    }
    queue<TreeNode*> treeQueue;
    int resDepth = 0;
    treeQueue.push(root);
    while (treeQueue.size()) {
        int size = treeQueue.size();
        resDepth ++;
        for (int i = 0; i < size; ++i) {
            TreeNode* tmp = treeQueue.front();
            treeQueue.pop();
            if (tmp->left != nullptr) {
                treeQueue.push(tmp->left);
            }
            if (tmp->right != nullptr) {
                treeQueue.push(tmp->right);
            }
        }
    }
    return resDepth;
}

}