有人可以解释一下这个状态机程序是如何工作的吗？

Question

我无法理解这个程序是如何工作的；有人可以解释一下吗？
我知道它与状态机有关，但我不明白状态机是如何工作的。

void abba();

int main()
{
    printf("Enter 10 characters, a or b.\n");
    abba();

    return 0;
}

void abba() 
{
    int x = 0;
    char  a;

    while ((scanf_s("%c", &a) == 1) && (a == 'a' || a == 'b')) {
        switch (x) {
        case 0:
            if (a == 'a')
                x = 1;
            break;
        case 1:
            if (a == 'b')
                x = 2;
            break;
        case 2:
            if (a == 'b')
                x = 3;
            else
                x = 1;
            break;
        case 3:
            if (a == 'b')
                x = 0;
            else {
                puts("abba is found !");
                x = 4;
            }
            break;
        }
    }
}

Answer 1

这是您的代码的状态机。

如您所见，有 4 个状态。

每个状态的解释

1. state 0 - If you receives char a you move to state 1 else you stay in the state 0.
2. state 1 - If you receives char b you move to state 2 else you stay in the state 1.
3. state 2 - If you receives char b you move to state 3 else you go back to state 1 from there again you need to read bb to reach state 3.
4. state 3 - If you receives char a you read complete abba else you need to read the input from the beginning.