a8

//Author: Jessica de Leeuw, deleeuwj
//Assignment 8 Quesion 1
#include <stdio.h> // imports IO library
#include <stdlib.h> // imports IO library
#include <string.h> // imports IO library
#define MAX_LEN 101

typedef struct node {
  char val[MAX_LEN];
  struct node * next;
} node_t;

void push(node_t * top, char * str);
char * pop(node_t * top, char pop_val[MAX_LEN]);

int main(void) {

  char str[MAX_LEN] = "*+AB-CD";
  int len = strlen(str);

  node_t * top = NULL;
  top = malloc(sizeof(node_t));

  for (int i = len; i > 0; i--) {
    char pop_val1[MAX_LEN];
    char pop_val2[MAX_LEN];
    if (str[i] == '*' || str[i] == '-' || str[i] == '+' || str[i] == '/') {
      pop(top, pop_val1);
      pop(top, pop_val2);
    }
    else {
      char char_str[2];
      char_str[0] = str[i];
      char_str[1] = '\0';
      push(top, char_str);
    }
    //printf("%c\n", str[i]);
  }

  return 0;

}

void push(node_t * top, char str[MAX_LEN]) {

  node_t * head = malloc(sizeof(node_t));
  if (head != NULL) {
    head->next = top;
    strcpy(head->val, str);
    // head->val = str;
    top = head;
  }
  else printf("%s could not be inserted. No memory available.\n", str);

}

char * pop(node_t * top, char pop_val[MAX_LEN]) {

  if (top->val != NULL) {
    node_t * tmp = top;
    strcpy(pop_val, top->val);
    strcpy(top->val, top->next->val);
    // pop_val = top->val;
    // top->val = top->next->val;
    free(tmp);
    return pop_val;
  }
  else {
    printf("The stack is empty.\n");
    return "\0";
  }

}