【剑指Offer】二叉树中和为某一值的路径

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题目

输入一棵二叉树和一个整数，打印出二叉树中结点值的和为输入整数的所有路径。从树的根结点开始往下一直到叶结点所经过的结点形成一条路径。

实现

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public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;
    }
}
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public ArrayList<ArrayList<Integer>> FindPath(TreeNode root, int target) {
    ArrayList<ArrayList<Integer>> paths = new ArrayList<>();
    ArrayList<Integer> path = new ArrayList<>();

    FindPath(root, target, 0, path, paths);

    return paths;
}

private void FindPath(TreeNode root, int target, int sum, ArrayList<Integer> path, ArrayList<ArrayList<Integer>> paths) {
    if (root == null)
        return;

    int currentSum = sum + root.val;
    path.add(root.val);

    if (currentSum == target && root.left == null && root.right == null)
        paths.add(new ArrayList(path));

    FindPath(root.left, target, currentSum, path, paths);
    FindPath(root.right, target, currentSum, path, paths);

    path.remove(path.size() - 1);
}