/** * Source : https://oj.leetcode.com/problems/minimum-depth-of-binary-tree/ * * * Given a binary tree, find its minimum depth. * * The minimum depth is the number of nodes along the shortest path from the root node * down to the nearest leaf node. */public class MinimumDepth {    /**     * 求出一棵二叉树的最小高度     *     * @param root     * @return     */    public int minDepth (TreeNode root) {        if (root == null) {            return 0;        }        int left = minDepth(root.leftChild);        int right = minDepth(root.rightChild);        if (left > right) {            return right + 1;        } else {            return left + 1;        }    }    public TreeNode createTree (char[] treeArr) {        TreeNode[] tree = new TreeNode[treeArr.length];        for (int i = 0; i < treeArr.length; i++) {            if (treeArr[i] == '#') {                tree[i] = null;                continue;            }            tree[i] = new TreeNode(treeArr[i]-'0');        }        int pos = 0;        for (int i = 0; i < treeArr.length && pos < treeArr.length-1; i++) {            if (tree[i] != null) {                tree[i].leftChild = tree[++pos];                if (pos < treeArr.length-1) {                    tree[i].rightChild = tree[++pos];                }            }        }        return tree[0];    }    private class TreeNode {        TreeNode leftChild;        TreeNode rightChild;        int value;        public TreeNode(int value) {            this.value = value;        }        public TreeNode() {        }    }    public static void main(String[] args) {        MinimumDepth minimumDepth = new MinimumDepth();        char[] arr0 = new char[]{'#'};        char[] arr1 = new char[]{'3','9','2','#','#','1','7'};        char[] arr2 = new char[]{'3','9','2','1','6','1','7','5'};        System.out.println(minimumDepth.minDepth(minimumDepth.createTree(arr0)));        System.out.println(minimumDepth.minDepth(minimumDepth.createTree(arr1)));        System.out.println(minimumDepth.minDepth(minimumDepth.createTree(arr2)));    }}