【数据结构与算法】一起搞定面试中的二叉树（一）

class TreeNode{
    int val;
    //左孩子
    TreeNode left;
    //右孩子
    TreeNode right;
}

int maxDeath(TreeNode node){
    if(node==null){
        return 0;
    }
    int left = maxDeath(node.left);
    int right = maxDeath(node.right);
    return Math.max(left,right) + 1;
}

int getMinDepth(TreeNode root){
    if(root == null){
        return 0;
    }
    return getMin(root);
}

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;
}

int numOfTreeNode(TreeNode root){
    if(root == null){
        return 0;
    }
    int left = numOfTreeNode(root.left);
    int right = numOfTreeNode(root.right);
    return left + right + 1;
}

int numsOfNoChildNode(TreeNode root){
    if(root == null){
        return 0;
    }
    if(root.left==null&&root.right==null){
        return 1;
    }
    return numsOfNodeTreeNode(root.left)+numsOfNodeTreeNode(root.right);
}

int numsOfkLevelTreeNode(TreeNode root,int k){
    if(root == null||k<1){
        return 0;
    }
    if(k==1){
        return 1;
    }
    int numsLeft = numsOfkLevelTreeNode(root.left,k-1);
    int numsRight = numsOfkLevelTreeNode(root.right,k-1);
    return numsLeft + numsRight;
}

boolean isBalanced(TreeNode node){
    return maxDeath2(node)!=-1;
}

int maxDeath2(TreeNode node){
    if(node == null){
        return 0;
    }
    int left = maxDeath2(node.left);
    int right = maxDeath2(node.right);
    if(left==-1||right==-1||Math.abs(left-right)>1){
        return -1;
    }
    return Math.max(left, right) + 1;
}

boolean isCompleteTreeNode(TreeNode root){
    if(root == null){
        return false;
    }
    Queue<TreeNode> queue = new LinkedList<TreeNode>();
    queue.add(root);
    boolean result = true;
    boolean hasNoChild = false;
    while(!queue.isEmpty()){
        TreeNode current = queue.remove();
        if(hasNoChild){
            if(current.left!=null||current.right!=null){
                result = false;
                break;
            }
        }else{
            if(current.left!=null&&current.right!=null){
                queue.add(current.left);
                queue.add(current.right);
            }else if(current.left!=null&&current.right==null){
                queue.add(current.left);
                hasNoChild = true;
            }else if(current.left==null&&current.right!=null){
                result = false;
                break;
            }else{
                hasNoChild = true;
            }
        }
    }
    return result;
}

boolean isSameTreeNode(TreeNode t1,TreeNode t2){
    if(t1==null&&t2==null){
        return true;
    }
    else if(t1==null||t2==null){
        return false;
    }
    if(t1.val != t2.val){
        return false;
    }
    boolean left = isSameTreeNode(t1.left,t2.left);
    boolean right = isSameTreeNode(t1.right,t2.right);
    return left&&right;
}

boolean isMirror(TreeNode t1,TreeNode t2){
    if(t1==null&&t2==null){
        return true;
    }
    if(t1==null||t2==null){
        return false;
    }
    if(t1.val != t2.val){
        return false;
    }
    return isMirror(t1.left,t2.right)&&isMirror(t1.right,t2.left);
}

TreeNode mirrorTreeNode(TreeNode root){
    if(root == null){
        return null;
    }
    TreeNode left = mirrorTreeNode(root.left);
    TreeNode right = mirrorTreeNode(root.right);
    root.left = right;
    root.right = left;
    return root;
}

TreeNode getLastCommonParent(TreeNode root,TreeNode t1,TreeNode t2){
    if(findNode(root.left,t1)){
        if(findNode(root.right,t2)){
        return root;
        }else{
            return getLastCommonParent(root.left,t1,t2);
        }
    }else{
        if(findNode(root.left,t2)){
            return root;
        }else{
        return getLastCommonParent(root.right,t1,t2)
        }
    }
}
    // 查找节点node是否在当前 二叉树中
boolean findNode(TreeNode root,TreeNode node){
    if(root == null || node == null){
        return false;
    }
    if(root == node){
        return true;
    }
    boolean found = findNode(root.left,node);
    if(!found){
        found = findNode(root.right,node);
    }
    return found;
}