LeetCode-Binary Tree Paths -解题报告

原题链接 https://leetcode.com/problems/binary-tree-paths/

Given a binary tree, return all root-to-leaf paths.

For example, given the following binary tree:

1
/   \
2     3
\
5

All root-to-leaf paths are:

["1->2->5", "1->3"]

打印出到叶子节点的路径。

dfs就行了，还有一点就是value可能是负数。

/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector<string> binaryTreePaths(TreeNode* root) {
flag = false;
dfs(root, "");
return ans;
}
void dfs(TreeNode* root, string path)
{
if (root == NULL)return;
if (root->left == NULL && root->right == NULL)
{
if (!flag)flag = true;
else path += "->";
ans.push_back(path + iTos(root->val));
return;
}
if (!flag)flag = true;
else path += "->";
path += iTos(root->val);
dfs(root->left, path);
dfs(root->right, path);

}
string iTos(int& val)
{
bool flag = true;
if (val < 0)flag = false, val = -val;
string str = "";
while (val)
{
str = (char((val % 10) + '0')) + str;
val /= 10;
}
if (!flag)str = "-" + str;
return str;
}
private:
bool flag;
vector<string>ans;
};