Unexpected result when using two different C++ compiler

I want to standardize the paragraph automatically when using dot (.)
For example :

.Agritour co von dieu le hai tram ti.Hien cong ty dang    .quan ly nhieu khach san .

After that, it would be

. Agritour co von dieu le hai tram ti. Hien cong ty dang. quan ly nhieu khach san.

But I have encountered an unexpected result between using two different compilers, Visual Studio 2019’s compiler (get the answer I need) and Dev-C++’s compiler (wrong result),

#include <iostream>
#include <string.h>
using namespace std;
#define MAX 300

void ChenChuoiTaiVitriK(char s[], char s1[], int k);
void Chuanhoa(char s[]);
int myStrlen(char s[], int k);
bool myStrcat(char s[], char s1[], char s2[]);
void myStrcpy(char s[], int vt, char s1[], int k);
int myStrstr(char s[], char s1[]);

int main()
{
    char s[MAX];
    fflush(stdin);
    cin.getline(s, MAX);
    char s1[MAX];
    myStrcpy(s1, 0, s, 0);
    Chuanhoa(s1);
    cout << s << endl << s1 << endl;
    return 0;
}
// delete element in array at index vt, k elements
void ChenChuoiTaiVitriK(char s[], int vt, int k) {
    int count = 0;
    if (s[vt + k] == '') {
        s[vt] = '';
    }
    else {
        for (int i = vt; s[i + k] != ''; i++) {
            s[i] = s[i + k];
            count = i + k;
        }
        s[count + 1 - k] = '';
    }
}
// dot standardization
void Chuanhoa(char s[]) {
    int count=0;
    char s3[MAX];
    myStrcpy(s3, 0, s, 0);
    for (int i = 0; s[i] != ''; i++) 
    {
        if (s[i] == ' ' && s[i + 1] == '.') {
            ChenChuoiTaiVitriK(s, i, 1);
            myStrcpy(s3, 0, s, 0);
            i-=2;
        }
        else if (s[i] == '.' && s[i + 1] == ' ' && s[i + 2] == '') {
            ChenChuoiTaiVitriK(s, i + 1, 1);
            myStrcpy(s3, 0, s, 0);
            i--;
        }
        else if (s[i] == '.' && s[i + 1] == ' ') {
            if (s[i + 2] == ' ') {
                ChenChuoiTaiVitriK(s, i + 1, 1);
                myStrcpy(s3, 0, s, 0);
                i -= 2;
            } 
        }
        else if (s[i] == '.' && s[i + 1] != ' ' && s[i + 1] != '') {
            for (int j = i +1; s3[j] != '';j++) {
                s[j+1]=s3[j];
            }
            s[i+1] = ' ';
            s[myStrlen(s3, 1) + 1] = '';
            myStrcpy(s3, 0, s, 0);
            i -= 2;
        }
    }
}
//copy a full C-string type from s[] 
void myStrcpy(char s1[], int vt, char s[], int k) {
    int count = 0;
    int flag = 0;
    for (int i = vt; s[i] != ''; i++) {
        s1[i] = s[i];
        count++;
        flag++;
    }
    s1[count] = '';
}
//return the size of string start from index k-1
int myStrlen(char s[], int k) {
    int count = 0;
    for (int i = k - 1; s[i] != ''; i++) 
    {
        count++;
    }
    return count;
}

So anyone can realize why and how i can fix that, i really appreciate that

VS2019 result:. Agritour co von dieu le hai tram ti. Hien cong ty dang. quan ly nhieu khach san.

DevC++ result:. Agritour co von dieu le hai tram ti.Hien cong ty dang .quan ly nhieu khach san .