leetcode笔记-Path Sum

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关于路径问题：

1.输出所有的路径

<pre name="code" class="cpp"> void findPath(vector<vector<int>> &ret,vector<int> tmp, TreeNode* root)    {        if(root==NULL) return;        tmp.push_back(root->val);        if(root->left == NULL && root->right == NULL)        {            ret.push_back(tmp);            return;        }        if(root->left!=NULL) findPath(ret,tmp,root->left);        if(root->right!=NULL) findPath(ret,tmp,root->right);        //tmp.pop_back();    }

//这个程序可以输出从根节点到任意叶节点的路径

2.关于路径和的问题

2.1 返回真假

class Solution {public:    bool hasPathSum(TreeNode* root, int sum) {        if(root==NULL) return false;        if(root->val==sum&&root->left==NULL&&root->right==NULL) return true;        return hasPathSum(root->left,sum-root->val)||hasPathSum(root->right,sum-root->val);    }    };

2.2 返回路径

<pre name="code" class="cpp">class Solution {public:    vector<vector<int>> pathSum(TreeNode* root, int sum) {        vector<vector<int>> ret;        vector<vector<int>> result;        vector<int> tmp;        findPath(ret,tmp,root);        while(!ret.empty())        {            vector<int> p;            int j=0;            p=ret.back();            cout<<p[1]<<endl;            for(int i=0;i<p.size();i++)            {                j=j+p[i];                cout<<p[i]<<endl;                //p.pop_back();                //cout<<j<<endl;            }            if(j==sum) result.push_back(p);            ret.pop_back();        }        return result;            }        void findPath(vector<vector<int>> &ret,vector<int> tmp, TreeNode* root)    {        if(root==NULL) return;        tmp.push_back(root->val);        if(root->left == NULL && root->right == NULL)        {            ret.push_back(tmp);            return;        }        if(root->left!=NULL) findPath(ret,tmp,root->left);        if(root->right!=NULL) findPath(ret,tmp,root->right);        //tmp.pop_back();    }};

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