package algorithm;

import algorithm.base.TreeNode;

import java.util.Stack;

public class FindTreeSumPath {

  /**
   * 二叉樹中和為某一值得路徑
   *
   * 1. 我們要把經過的路徑上的結點都保存起來，也就是需要一個輔助棧stack;
   * 2. 通過前序遍歷找到末尾節點，當發現是葉子節點時判斷是否總和是否是給定值sum；如果是即找到一條路徑
   * 3. 當遍歷到根節點，發現不是符合要求的路徑時，要從stack中pop()出當前節點。
   */
  public static void findPath(TreeNode<Integer> node, int sum) {
    if (node == null) return;
    Stack<Integer> stack = new Stack<>();
    findPathImpl(node, sum, stack);
  }

  public static void findPathImpl(TreeNode<Integer> node, int sum, Stack<Integer> path) {
    if (node == null) return;
    if (node.leftNode == null && node.rightNode == null) {
      if (node.value == sum) {
        System.out.println("找到一個路徑：");
        for (int val : path) {
          System.out.print(val + " + ");
        }
        System.out.println(node.value + " .");
      }
    } else {
      path.add(node.value);
      int curVal = node.value;
      findPathImpl(node.leftNode, sum - curVal, path);
      findPathImpl(node.rightNode, sum - curVal, path);
      path.pop();
    }
  }

  public static void main(String[] args) {
    TreeNode<Integer> node1 = new TreeNode<>(10);
    TreeNode<Integer> node2 = new TreeNode<>(5);
    TreeNode<Integer> node3 = new TreeNode<>(12);
    TreeNode<Integer> node4 = new TreeNode<>(4);
    TreeNode<Integer> node5 = new TreeNode<>(7);
    node1.leftNode = node2;
    node1.rightNode = node3;
    node2.leftNode = node4;
    node2.rightNode = node5;

    findPath(node1, 22);
  }
}

package algorithm.base;

public class TreeNode<T> {
  public T value;
  public TreeNode leftNode;
  public TreeNode rightNode;

  public TreeNode(T value) {
    this.value = value;
    leftNode = null;
    rightNode = null;
  }
}