C言語のきほん「オートマトンの動作をシミュレートする」

//オートマトンの動作をシミュレートするプログラム

#include <stdio.h>
#include <string.h>

// 状態を列挙型で定義
typedef enum { S1, S2, S3 } State;

int main() {
    char input[] = "0011001110";
    char output[sizeof(input)] = "";
    State state = S1;

    for (int i = 0; i < strlen(input); i++) {
        char symbol = input[i];

        switch (state) {
            case S1:
                if (symbol == '0') {
                    output[i] = '0';
                    state = S1;
                } else if (symbol == '1') {
                    output[i] = '0';
                    state = S2;
                }
                break;

            case S2:
                if (symbol == '0') {
                    output[i] = '0';
                    state = S1;
                } else if (symbol == '1') {
                    output[i] = '1';
                    state = S3;
                }
                break;

            case S3:
                if (symbol == '0') {
                    output[i] = '0';
                    state = S1;
                } else if (symbol == '1') {
                    output[i] = '1';
                    state = S3;
                }
                break;
        }
    }

    printf("入力列: %s\n", input);
    printf("出力列: %s\n", output);

    return 0;
}