recursive

#pragma warning (disable: 4996) //visual studio bug fix, no need on code

#include <stdio.h> //printf
#include <stdlib.h> //malloc

int isValid(const char* argument, int length) {
    for (int i = 0; i < length; i++) {
        if (argument[i] == '?' ||
            i > 0 && i < length - 1 && argument[i - 1] == argument[i] && argument[i] == argument[i + 1])
            return 0; //0 == false
    }
    return 1; //1 == true
}

void printAllBinaryStrings(char* input, int length, const char* toPrint, const int lengthConst) {
    for (int i = 0; i < length; i++) {
        if (input[i] == '?') {
            input[i] = '0';
            printAllBinaryStrings(input + i, length - i, toPrint, lengthConst);
            input[i] = '1';
            printAllBinaryStrings(input + i, length - i, toPrint, lengthConst);
            input[i] = '?'; //important!
        }

        if (isValid(toPrint, lengthConst) == 1)
            printf("%s\n", toPrint);
    }
}

int main() {
    int length = 0;

    scanf("%d", &length);

    ++length; //add '\0'

    char* input = (char*)malloc(sizeof(char) * length);

    scanf("%s", input);

    printAllBinaryStrings(input, --length, input, length);

    free(input);
}