initializer list cannot be

inferred for array type

这个错误通常出现在使用 C++11 中的初始化列表初始化数组时，编译器无法推断出数组的大小。例如：

int arr[] = {1, 2, 3}; // 编译器无法推断出数组的大小

解决方法是显式指定数组的大小，例如：

int arr[3] = {1, 2, 3}; // 显式指定数组的大小为 3

或者使用 C++11 中的 std::array 容器，例如：

#include <array>
std::array<int, 3> arr = {1, 2, 3}; // 使用 std::array 容器

相关问题

Cannot invoke "java.util.ArrayList.isEmpty()" because "list" is null

This error message means that you are trying to call the isEmpty() method on an ArrayList object that is null, meaning it has not been initialized or assigned to any value. It is important to make sure that you have properly initialized the ArrayList object before calling any of its methods.

To fix this error, you should first check if the ArrayList object is null before calling the isEmpty() method. You can do this using an if-statement:

if (list != null && !list.isEmpty()) {
    // list is not null and not empty, do something
} else {
    // list is null or empty, handle the error
}

Alternatively, you can initialize the ArrayList object with an empty list when you declare it:

ArrayList<String> list = new ArrayList<>();

This way, even if you forget to add any elements to the list, it will not be null and you can call its methods without any errors.

The 18th China Jiliang University Programming Contest is approaching, Little Gyro wants to send plenty of messages by e-mail to invite people participating in the competition. However, Little Gyro only has one e-mail account (acm309@126.com) to send these messages. In order to invite more candidates as possible, Little Gyro needs your help. Given the whole time table of the e-mail messages Little Gyro wants to send, including the start time and the end time of each message, and it usually doesn’t take the same time when Little Gyro sending different e-mail messages. Besides, Little Gyro cannot send two or more messages at the same time. That means Little Gyro can send the next message only if the start time after the end time of the previous one. Now Little Gyro wants to know how many e-mail messages he can send to the competition candidates at most.

This problem can be solved using a greedy algorithm. First, we need to sort the messages by their end time in ascending order. Then, we can start sending messages from the earliest end time to the latest end time, and choose the message with the earliest start time that doesn't conflict with the previously sent messages. This ensures that we can send the maximum number of messages without conflicts.

Here is the pseudocode for the algorithm:

1. Sort the messages by their end time in ascending order.
2. Initialize a variable count to 0.
3. Initialize a variable prev_end to 0.
4. For each message in the sorted list:
a. If the start time of the message is greater than or equal to prev_end,
increment count and update prev_end to the end time of the message.
5. Return count.

The time complexity of this algorithm is O(nlogn), where n is the number of messages. This is due to the sorting step. The rest of the algorithm takes linear time.

Here is the Python code for the algorithm:

def max_emails(messages):
    messages.sort(key=lambda x: x[1])  # sort by end time
    count = 0
    prev_end = 0
    for start, end in messages:
        if start >= prev_end:
            count += 1
            prev_end = end
    return count

We can call the function with a list of tuples representing the start and end times of the messages:

messages = [(1, 3), (2, 5), (4, 7), (6, 9), (8, 10)]
print(max_emails(messages))  # output: 3

In this example, we can send at most 3 messages without conflicts.