代码随想录算法训练营第十八天|● 513.找树左下角的值● 112. 路径总和 113.路径总和ii-优快云博客

本文链接：https://blog.youkuaiyun.com/minodeer/article/details/137060551

513.找树左下角的值

class Solution {
public:
    int ret = -1;
    int ans=1;
    void dg(TreeNode* node, int step) {
        if (node->left != NULL) {
            if (node->left->right == NULL && node->left->left == NULL) {
                if (step > ret) {
                    ret = step;
                    ans = node->left->val;
                }
            }
            if (node->right != NULL) {
                
                if (node->right->right == NULL && node->right->left == NULL) {

                    if (step > ret) {
                        ret = step;
                        ans = node->right->val;
                    }
                }
            }

            if (node->left) {
                step++;
                dg(node->left, step);
                step--;
            }
            if (node->right) {
                step++;
                dg(node->right, step++);
                step--;
            }
        }
        return;
    }
    int findBottomLeftValue(TreeNode* root) {
        dg(root, 0);
        if (root->left == NULL && root->right == NULL)
            return root->val;
        if()
        return ans;
    }
};

112. 路径总和

class Solution {
public:
    int flag;
    int target;
    bool dfs(TreeNode* node, int count) {
        if (!node->left && !node->right) {
            if (count == target)
                return 1;
            return 0;
        }
        if (node->left) {
            if (dfs(node->left, count + node->left->val))
                return 1;
        }
        if (node->right) {

            if (dfs(node->right, count + node->right->val))
                return 1;
        }
        return 0;
    }

    bool hasPathSum(TreeNode* root, int targetSum) {
        if (root == NULL)
            return 0;
        target = targetSum;
        return dfs(root, root->val);   
    }
};

113.路径总和ii

class Solution {
public:
    vector<vector<int>> ret;
    vector<int> ans;
    int target;
    void dfs(TreeNode* node, int count) {
        if (!node->left && !node->right) {
            if (count == target) {
                ret.push_back(ans);
            }
            return;
        }
        if (node->left) {
            ans.push_back(node->left->val);
            dfs(node->left, count + node->left->val);
            ans.pop_back();
        }
        if (node->right) {
            ans.push_back(node->right->val);
            dfs(node->right, count + node->right->val);
            ans.pop_back();
        }
        return;
    }
    vector<vector<int>> pathSum(TreeNode* root, int targetSum) {
        if (root == NULL)
            return {};
        target = targetSum;
        ans.push_back(root->val);
        dfs(root, root->val);
        return ret;
    }
};