Transform the Expression

#include <stdio.h>
#include <ctype.h>

char token[1000];
char stack[1000];
char *sp = stack;

void getToken(){
    char c;
    int i;
    for(i = 0; (c = getchar()) != '\n'; i++)
        token[i] = c;
    token[i] = '\0';
    return;
}

int isop(char *p){
    if(!islower(*p) && *p != '(' && *p != ')')
        return 1;
    else
        return 0;
}

inline int fastint(){
    int r = 0;
    char c = getchar();
    while(c == '\n')
        c = getchar();
    while(c != '\n'){
        r = (r*10) + (c - '0');
        c = getchar();
    }
    return r;
}

void push(char *p){
    if(sp <= (stack+1000))
        *sp++ = *p;
    return;
}

void pop(){
    if((sp - stack) >= 0)
        putchar(*--sp);
    else
        return;
}

char *expression(char *p){
    while(*p != ')' && *p != '\0') {
        if(isalpha(*p) && !isspace(*p))
            putchar(*p);
        else if(isop(p))
            push(p);
        else if(*p == '('){
            p = expression(++p);
        }
        p++;
    }
    pop();
    return p;
}

int main(){
    int i = fastint();

    while(i){
        getToken();
        expression(token);
        putchar('\0');
        putchar('\n');
        i--;
    }
    return 0;
}