LintCode 376 - Binary Tree Path Sum


https://xuezhashuati.blogspot.com/2016/02/binary-tree-path-sum.html
Given a binary tree, find all paths that sum of the nodes in the path equals to a given number target.

A valid path is from root node to any of the leaf nodes.


Example
Given a binary tree, and target = 5:

     1
    / \
   2   4
  / \
 2   3
return

[
  [1, 2, 2],
  [1, 4]
]
public List<String> binaryTreePaths(TreeNode root) { List<String> result = new ArrayList<>(); List<Integer> list = new ArrayList<>(); if (root == null) { return result; } list.add(root.val); helper(root, list, result); return result; } private void helper(TreeNode root, List<Integer> list, List<String> result) { if (root.left == null && root.right == null) { result.add(toStr(new ArrayList<Integer>(list))); } if (root.left != null) { list.add(root.left.val); helper(root.left, list, result); list.remove(list.size() - 1); } if (root.right != null) { list.add(root.right.val); helper(root.right, list, result); list.remove(list.size() - 1); } } private String toStr(List<Integer> list) { StringBuilder sb = new StringBuilder(); sb.append(list.get(0)); for (int i = 1; i < list.size(); i++) { sb.append("->"); sb.append(list.get(i)); } return sb.toString(); }

DFS + Backtracking从root往下遍历。如果发现sum == target并且已经走到底了,就把这坨序列加到result里。
    public List<List<Integer>> binaryTreePathSum(TreeNode root, int target) {
        // Write your code here
        List<List<Integer>> result = new ArrayList<>();
        List<Integer> list = new ArrayList<>();
        if (root == null) {
            return result;
        }
        
        list.add(root.val);
        helper(root, target, result, list, root.val);
        return result;
    }
    
    public void helper(TreeNode root, 
                       int target, 
                       List<List<Integer>> result, 
                       List<Integer> list, 
                       int sum) {
                           
        if (root == null) {
            return;
        }
        
        if (root.left == null && root.right == null && sum == target) {
            result.add(new ArrayList<Integer>(list));
            return;
        }
        
        if (root.left != null) {
            list.add(root.left.val);
            helper(root.left, target, result, list, sum + root.left.val);
            list.remove(list.size() - 1);
        }
        
        if (root.right != null) {
            list.add(root.right.val);
            helper(root.right, target, result, list, sum + root.right.val);
            list.remove(list.size() - 1);
        }
    }
http://blog.csdn.net/jason__liang/article/details/64165887
static public List<List<Integer>> binaryTreePathSum(TreeNode root, int target) { // Write your code here List<List<Integer>> ret=new ArrayList<>(); ArrayList<Integer> linshi=new ArrayList<>(); int sum=root.val; preordertravel(root,ret,target,linshi,sum); return ret; } static void preordertravel(TreeNode root,List<List<Integer>> ret,int target,ArrayList<Integer> linshi,int sum) { if(sum==target&&root!=null&&root.left==null&&root.right==null) { linshi.add(root.val); ret.add(new ArrayList<>(linshi)); linshi.remove(linshi.size()-1); } else { if(root!=null) { linshi.add(root.val); preordertravel(root.left, ret, target, linshi, root.left==null?sum:sum+root.left.val); preordertravel(root.right, ret, target, linshi, root.right==null?sum:sum+root.right.val); linshi.remove(linshi.size()-1); } } }

public List<String> binaryTreePaths(TreeNode root) { List<String> result = new ArrayList<>(); if (root == null) { return result; } List<String> left = binaryTreePaths(root.left); List<String> right = binaryTreePaths(root.right); for (String l : left) { result.add(root.val + "->" + l); } for (String r : right) { result.add(root.val + "->" + r); } if (result.size() == 0) { result.add("" + root.val); } return result; }

Labels

LeetCode (1432) GeeksforGeeks (1122) LeetCode - Review (1067) Review (882) Algorithm (668) to-do (609) Classic Algorithm (270) Google Interview (237) Classic Interview (222) Dynamic Programming (220) DP (186) Bit Algorithms (145) POJ (141) Math (137) Tree (132) LeetCode - Phone (129) EPI (122) Cracking Coding Interview (119) DFS (115) Difficult Algorithm (115) Lintcode (115) Different Solutions (110) Smart Algorithm (104) Binary Search (96) BFS (91) HackerRank (90) Binary Tree (86) Hard (79) Two Pointers (78) Stack (76) Company-Facebook (75) BST (72) Graph Algorithm (72) Time Complexity (69) Greedy Algorithm (68) Interval (63) Company - Google (62) Geometry Algorithm (61) Interview Corner (61) LeetCode - Extended (61) Union-Find (60) Trie (58) Advanced Data Structure (56) List (56) Priority Queue (53) Codility (52) ComProGuide (50) LeetCode Hard (50) Matrix (50) Bisection (48) Segment Tree (48) Sliding Window (48) USACO (46) Space Optimization (45) Company-Airbnb (41) Greedy (41) Mathematical Algorithm (41) Tree - Post-Order (41) ACM-ICPC (40) Algorithm Interview (40) Data Structure Design (40) Graph (40) Backtracking (39) Data Structure (39) Jobdu (39) Random (39) Codeforces (38) Knapsack (38) LeetCode - DP (38) Recursive Algorithm (38) String Algorithm (38) TopCoder (38) Sort (37) Introduction to Algorithms (36) Pre-Sort (36) Beauty of Programming (35) Must Known (34) Binary Search Tree (33) Follow Up (33) prismoskills (33) Palindrome (32) Permutation (31) Array (30) Google Code Jam (30) HDU (30) Array O(N) (29) Logic Thinking (29) Monotonic Stack (29) Puzzles (29) Code - Detail (27) Company-Zenefits (27) Microsoft 100 - July (27) Queue (27) Binary Indexed Trees (26) TreeMap (26) to-do-must (26) 1point3acres (25) GeeksQuiz (25) Merge Sort (25) Reverse Thinking (25) hihocoder (25) Company - LinkedIn (24) Hash (24) High Frequency (24) Summary (24) Divide and Conquer (23) Proof (23) Game Theory (22) Topological Sort (22) Lintcode - Review (21) Tree - Modification (21) Algorithm Game (20) CareerCup (20) Company - Twitter (20) DFS + Review (20) DP - Relation (20) Brain Teaser (19) DP - Tree (19) Left and Right Array (19) O(N) (19) Sweep Line (19) UVA (19) DP - Bit Masking (18) LeetCode - Thinking (18) KMP (17) LeetCode - TODO (17) Probabilities (17) Simulation (17) String Search (17) Codercareer (16) Company-Uber (16) Iterator (16) Number (16) O(1) Space (16) Shortest Path (16) itint5 (16) DFS+Cache (15) Dijkstra (15) Euclidean GCD (15) Heap (15) LeetCode - Hard (15) Majority (15) Number Theory (15) Rolling Hash (15) Tree Traversal (15) Brute Force (14) Bucket Sort (14) DP - Knapsack (14) DP - Probability (14) Difficult (14) Fast Power Algorithm (14) Pattern (14) Prefix Sum (14) TreeSet (14) Algorithm Videos (13) Amazon Interview (13) Basic Algorithm (13) Codechef (13) Combination (13) Computational Geometry (13) DP - Digit (13) LCA (13) LeetCode - DFS (13) Linked List (13) Long Increasing Sequence(LIS) (13) Math-Divisible (13) Reservoir Sampling (13) mitbbs (13) Algorithm - How To (12) Company - Microsoft (12) DP - Interval (12) DP - Multiple Relation (12) DP - Relation Optimization (12) LeetCode - Classic (12) Level Order Traversal (12) Prime (12) Pruning (12) Reconstruct Tree (12) Thinking (12) X Sum (12) AOJ (11) Bit Mask (11) Company-Snapchat (11) DP - Space Optimization (11) Dequeue (11) Graph DFS (11) MinMax (11) Miscs (11) Princeton (11) Quick Sort (11) Stack - Tree (11) 尺取法 (11) 挑战程序设计竞赛 (11) Coin Change (10) DFS+Backtracking (10) Facebook Hacker Cup (10) Fast Slow Pointers (10) HackerRank Easy (10) Interval Tree (10) Limited Range (10) Matrix - Traverse (10) Monotone Queue (10) SPOJ (10) Starting Point (10) States (10) Stock (10) Theory (10) Tutorialhorizon (10) Kadane - Extended (9) Mathblog (9) Max-Min Flow (9) Maze (9) Median (9) O(32N) (9) Quick Select (9) Stack Overflow (9) System Design (9) Tree - Conversion (9) Use XOR (9) Book Notes (8) Company-Amazon (8) DFS+BFS (8) DP - States (8) Expression (8) Longest Common Subsequence(LCS) (8) One Pass (8) Quadtrees (8) Traversal Once (8) Trie - Suffix (8) 穷竭搜索 (8) Algorithm Problem List (7) All Sub (7) Catalan Number (7) Cycle (7) DP - Cases (7) Facebook Interview (7) Fibonacci Numbers (7) Flood fill (7) Game Nim (7) Graph BFS (7) HackerRank Difficult (7) Hackerearth (7) Inversion (7) Kadane’s Algorithm (7) Manacher (7) Morris Traversal (7) Multiple Data Structures (7) Normalized Key (7) O(XN) (7) Radix Sort (7) Recursion (7) Sampling (7) Suffix Array (7) Tech-Queries (7) Tree - Serialization (7) Tree DP (7) Trie - Bit (7) 蓝桥杯 (7) Algorithm - Brain Teaser (6) BFS - Priority Queue (6) BFS - Unusual (6) Classic Data Structure Impl (6) DP - 2D (6) DP - Monotone Queue (6) DP - Unusual (6) DP-Space Optimization (6) Dutch Flag (6) How To (6) Interviewstreet (6) Knapsack - MultiplePack (6) Local MinMax (6) MST (6) Minimum Spanning Tree (6) Number - Reach (6) Parentheses (6) Pre-Sum (6) Probability (6) Programming Pearls (6) Rabin-Karp (6) Reverse (6) Scan from right (6) Schedule (6) Stream (6) Subset Sum (6) TSP (6) Xpost (6) n00tc0d3r (6) reddit (6) AI (5) Abbreviation (5) Anagram (5) Art Of Programming-July (5) Assumption (5) Bellman Ford (5) Big Data (5) Code - Solid (5) Code Kata (5) Codility-lessons (5) Coding (5) Company - WMware (5) Convex Hull (5) Crazyforcode (5) DFS - Multiple (5) DFS+DP (5) DP - Multi-Dimension (5) DP-Multiple Relation (5) Eulerian Cycle (5) Graph - Unusual (5) Graph Cycle (5) Hash Strategy (5) Immutability (5) Java (5) LogN (5) Manhattan Distance (5) Matrix Chain Multiplication (5) N Queens (5) Pre-Sort: Index (5) Quick Partition (5) Quora (5) Randomized Algorithms (5) Resources (5) Robot (5) SPFA(Shortest Path Faster Algorithm) (5) Shuffle (5) Sieve of Eratosthenes (5) Strongly Connected Components (5) Subarray Sum (5) Sudoku (5) Suffix Tree (5) Swap (5) Threaded (5) Tree - Creation (5) Warshall Floyd (5) Word Search (5) jiuzhang (5)

Popular Posts