Implement the Strtoint function yourself

int Strtoint (const char*pstr,int defaultval) {//NULL pointer access if (pstr==0) return defaultval;
    int result=1,tem=0;
    Number of digits int bitnum=0;
    symbol int sign=1;
    const char *PTEM=PSTR;
        Detects whether the first character is-or the number if (*ptem== '-') {sign=-1;
                Whether it is at the end or in the middle there is ' if ' ((*++ptem)!=0) {if (*ptem> ' 0 ' &&*ptem<= ' 9 ') {
                -1 *=n result*= (*ptem-' 0 ');
            Calculate the number of bits bitnum= (strlen (PSTR)-2);
            } else {return defaultval;
        }} else {return defaultval;
        }} else if (*ptem> ' 0 ' &&*ptem<= ' 9 ') {result= (*ptem-' 0 ');
    Calculate the number of bits bitnum= (strlen (PSTR)-1);
    } else {return defaultval;
    } ptem++; Detects that the remainder of the string has no illegal ' *ptem!=0 ' truncation while (a) {///illegal if (*ptem< ' 0 ' | | *ptem> ' 9') return defaultval;
        Calculation results Tem=tem*10+n tem=tem*10+ (*ptem-' 0 ');
    ptem++;
}//combination first and subsequent digits return (Tem+result*pow (10,bitnum)) *sign; }