572. 另一棵树的子树

给你两棵二叉树 root 和 subRoot 。检验 root 中是否包含和 subRoot 具有相同结构和节点值的子树。如果存在，返回 true ；否则，返回 false 。

二叉树 tree 的一棵子树包括 tree 的某个节点和这个节点的所有后代节点。tree 也可以看做它自身的一棵子树。

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/subtree-of-another-tree
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

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class Solution {
    private boolean solve(TreeNode root, TreeNode subRoot) {
        if (root == null) {
            return false;
        }
        return check(root, subRoot) || solve(root.left, subRoot) || solve(root.right, subRoot);
    }

    private boolean check(TreeNode root, TreeNode subRoot) {
        if (root == null && subRoot == null) {
            return true;
        }

        if (root == null || subRoot == null) {
            return false;
        }

        return root.val == subRoot.val && check(root.left, subRoot.left) && check(root.right, subRoot.right);
    }

    public boolean isSubtree(TreeNode root, TreeNode subRoot) {
        return solve(root, subRoot);
    }
}

class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;

    TreeNode() {
    }

    TreeNode(int val) {
        this.val = val;
    }

    TreeNode(int val, TreeNode left, TreeNode right) {
        this.val = val;
        this.left = left;
        this.right = right;
    }
}

KMP

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;

class Solution {

    private void getOrder(TreeNode root, List<Integer> orders) {
        if (root == null) {
            orders.add(null);
            return;
        }
        orders.add(root.val);
        getOrder(root.left, orders);
        getOrder(root.right, orders);
    }

    private int[] getNext(List<Integer> list) {
        int[] next = new int[list.size()];
        next[0] = -1;
        int i = 0, j = -1;
        while (i < list.size() - 1) {
            if (j == -1 || Objects.equals(list.get(i), list.get(j))) {
                ++i;
                ++j;
                if (Objects.equals(list.get(i), list.get(j))) {
                    next[i] = next[j];
                } else {
                    next[i] = j;
                }
            } else {
                j = next[j];
            }
        }

        return next;
    }

    private boolean match(List<Integer> l1, List<Integer> l2) {
        int[] next = getNext(l2);
        int i = 0, j = 0;
        while (i < l1.size() && j < l2.size()) {
            if (j == -1 || Objects.equals(l1.get(i), l2.get(j))) {
                ++i;
                ++j;
            } else {
                j = next[j];
            }
        }
        return j == l2.size();
    }

    public boolean isSubtree(TreeNode root, TreeNode subRoot) {
        List<Integer> l1 = new ArrayList<>();
        getOrder(root, l1);
        List<Integer> l2 = new ArrayList<>();
        getOrder(subRoot, l2);
        return match(l1, l2);
    }
}


class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;

    TreeNode() {
    }

    TreeNode(int val) {
        this.val = val;
    }

    TreeNode(int val, TreeNode left, TreeNode right) {
        this.val = val;
        this.left = left;
        this.right = right;
    }
}