leetcode — minimum-depth-of-binary-tree

/**
* 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)));
}
}