gistfile1.java

public int minDepth(TreeNode root) {
    if(root == null) return 0;
    int level = 1;
    return  minDeptRe(root, level);
}

public int minDeptRe(TreeNode root, int level){
    if(root.left == null && root.right == null)
        return level;
        
    int leftMinLevel=0;
    int rightMinLevel=0;
    
   /* if(root.left != null){//does not affect the running time
        if(root.left.left == null && root.left.right == null)
            return ++level;
    }
    
    if(root.right != null){
        if(root.right.left == null && root.right.right == null)
            return ++level;
    }*/
    
    if(root.left != null){
        leftMinLevel = minDeptRe(root.left, level+1);
    }
    
    if(root.right != null){
        rightMinLevel = minDeptRe(root.right, level+1);
    }
    if(leftMinLevel==0) return rightMinLevel;
    if(rightMinLevel==0) return leftMinLevel;
    
    return Math.min(leftMinLevel, rightMinLevel);
    
};