leetcode-String to Integer (atoi)

int myAtoi(char* str) {
    int y=0,s=0;
    while(*str!='\0'){
        if(*str==' '||*str=='\t') {
            str++;continue;
        }else if(*str=='-'){
            s=1;*str++;break;
        }else if(*str=='+'){
            s=0;*str++;break;
        }
        break;
    }
    while(*str!='\0'&&*str<='9'&&*str>='0'){
        //printf("%c,%d\n",*str,y);
        if(y<=(INT_MAX/10)){
            y=y*10; 
        }else{
            if(s==1) return INT_MIN;
            return INT_MAX;
        }
        if((*str-'0')>(INT_MAX-y)){
            if(s==1) return INT_MIN;
            return INT_MAX;
        }else{
            y+=(*str-'0');
        }
        *str++;
    }
    if(s==0)
        return y;
    return 0-y;
}