Program that uses this DFA and validates whether an entered string is valid float or not

Code for Program that uses this DFA and validates whether an entered string is valid float or not in C++ Programming

#include <iostream.h>
#include <stdio.h>
#include <conio.h>
#include <ctype.h>
#include <process.h>

int main()
{
    int flag = 0;
    char ch = NULL;
    char state = '0';
    char token[20] = {NULL};
    char stt[5][3] = {NULL, '4', '5',
            '0', '1', '2',
            '1', '1', '2',
            '2', '3', NULL,
            '3', '3', NULL};

    cout<<"Input float data : ";
    cin>>token;

    for(int i=0; token[i] != NULL; i++)
    {
        if(isdigit(token[i]))
        {
            ch = '4';
        }
        elseif (token[i] == '.')
        {
            ch = '5';
        }
        else
        {
            flag=1;
            printf("Invalide value");
            break;
        }

        for(int j=1; j<3 && ch != stt[0][j]; j++);
        for(int k=1; k<5 && state != stt[k][0]; k++);
        state =stt[k][j];
        if(state==NULL)
        {
            flag=1;
            printf("Invalide value");
            break;
        }
    }
    if(flag==0)
    {
        printf("Valide value");
    }
    getch();
    return 0;
}