111. Minimum Depth of Binary Tree

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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.

Solution 1 DFS

1ms 12.55

public class Solution {    public int minDepth(TreeNode root) {        if(root == null){            return 0;        }        return getMin(root);    }    public int getMin(TreeNode root){        if(root == null){            return Integer.MAX_VALUE;        }        if(root.left == null && root.right == null){            return 1;        }        return Math.min(getMin(root.left), getMin(root.right)) + 1;    }}

Solution 2 BFS

public class Solution {    public int minDepth(TreeNode root) {        if(root == null){            return 0;        }        Queue<TreeNode> q = new LinkedList<TreeNode>();        int depth = 1;        q.offer(root);        while(!q.isEmpty()){            int size = q.size();            for(int i = 0; i < size; i++){                TreeNode temp = q.poll();                if(temp.left != null){                    q.offer(temp.left);                }                if(temp.right != null){                    q.offer(temp.right);                }                if(temp.left == null && temp.right == null){                    return depth;                }            }            depth++;        }        return depth;    }}

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