Trim in C++

trimfn.cpp

#include<iostream>
#include<cstring>

char* trim(char* str);
int main(){
    return 1;

}

char* trim(char* str){
    char *ret;
    int tCa = 0; //totalCharAllocated
    ret =  new char[strlen(str)]; //need to implement the function
    
    bool check_first_space = false;
    int num_spaces_current = 0;
    while(*str!='\0'){
        //iterate through the string
        if((*str>=65 && *str<=91) || (*str>=97 && *str<=123)
||(*str=='+') ||(*str=='-')){
            if(!check_first_space) check_first_space = true;
            num_spaces_current = 0;
            cout<<*str;
            *ret = *str;
             ret++; tCa++;

        } else if(*str==' '){
            num_spaces_current++;
            if(num_spaces_current==1){
                if(check_first_space)
                cout<<' ';
                *ret = *str;
                 ret++; tCa++;
                // need to figure out things
            }
        } else {
            num_spaces_current++;
        }
        str++;
    }
    
    char *returning = new char[tCa];
    strncpy(returning, ret, tCa);
    delete []ret;
    return returning;
}