leetcode TreeNode实现

class TreeNode {
public int val;
public TreeNode left;
public TreeNode right;
TreeNode(int x) { val = x; }
@Override
public String toString(){
    return Integer.toString(val);
}

// int []arr = {3, 9, 20, Integer.MAX_VALUE, Integer.MAX_VALUE, 15, 7};
private static int[] StrToIntArray(String str) {
    str = str.substring(1, str.length() - 1);
    String []strs = str.split(",");
    int []arr = new int[strs.length];

    for (int i = 0; i < arr.length; i++) {
        if (strs[i].equals("null")) {
            arr[i] = Integer.MAX_VALUE;
        } else {
            arr[i] = Integer.parseInt(strs[i]);
        }
    }

    return arr;
}

// String str = "[3,9,20,null,null,15,7]";
public static TreeNode mkTree(String str) {

    int []arr = StrToIntArray(str);
    TreeNode []nodes = new TreeNode[arr.length + 1];
    for (int i = 1; i < nodes.length; i++) {
        if (arr[i - 1] != Integer.MAX_VALUE) {
            nodes[i] = new TreeNode(arr[i - 1]);
        }else {
            nodes[i] = null;
        }
    }

    TreeNode node = null;
    for (int i = 1; i <= nodes.length / 2; i++) {
        node = nodes[i];
        if (node == null) {
            continue;
        }
        node.left = 2*i<nodes.length?nodes[2 * i]:null;
        node.right = 2 * i + 1<nodes.length?nodes[2 * i + 1]:null;
    }
    return nodes[1];
}

}
本文转载自https://www.cnblogs.com/kungfupanda/p/11223633.html
在原来的基础上修改了一些，原来"[1,2,3,4]"这样的未能实现