View difference between Paste ID: UVRYSZiK and VifrP6cF

 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <ctype.h>
 
 #define STACKSIZE 250
 
 typedef struct{
         int top;
         long long int items[STACKSIZE];
         }STACK;
 
 
 void push(long long int x, STACK *ps);
 int pop(STACK *ps);
 int ispositivedigit(char* input);
-int isnegativedigit(char* input); //function for detection negative numbers
+int isnegativedigit(char* input);  // function for detection negative numbers
-void printtop(STACK *ps); //bonus
+void printtop(STACK *ps);  // bonus
 
 
 
 int main()
-    char input[1024]; //array for loaded values
+
     char input[1024];  // array for loaded values
-    int end = 1; //detects end of input
+
-    int count = 0; //variable for detection if no arguments were enetred
+    int end = 1;  // detects end of input
     int count = 0;  // variable for detection if no arguments were enetred
     STACK ps = {0, {0}};
     long long int number, a, b, result, printresult;
 
 
     while (end != EOF) {
 
         // Read next token
         end = scanf("%s", input);
         count += 1;
         if(end == EOF) {
             count -= 1;
             break;
-        //if it's a positive numebr
+
-        if (ispositivedigit(input) == 1) {
+
-            number = atoll(input); //converts string to long long int
+        // If it's a numebr
-            push(number, &ps); //add a number to the top of the stack
+        if (ispositivedigit(input) || isnegativedigit(input)) {
             number = atoll(input);  // converts string to long long int
             push(number, &ps);  // add a number to the top of the stack
-            //string is a negative number or invalid input
+
-            if (strlen(input) > 1) {
+        // It it's an operator
-                if (isnegativedigit(input) == 1) {
+        else if (isoperator(input)) {
-                    number = atoll(input);
+            // p
-                    push(number, &ps);
+            if (strcmp(input, "p") == 0) {
                 printtop(&ps);
-                else {
+
-                    fprintf(stderr, "Error: Invalid input!\n");
+            // +
             else if (strcmp(input, "+") == 0) {
                 a=pop(&ps); b=pop(&ps);
                 result = a + b;
                 push(result, &ps);
             }
-            if (strlen(input) == 1) {
+            // -
-                if (strcmp(input, "p") == 0) {
+            else if (strcmp(input, "+") == 0) {
-                    printtop(&ps);
+                a=pop(&ps); b=pop(&ps);
                 result = a - b;
-                else {
+                push(result, &ps);
             }
-                    a=pop(&ps);
+            // *
-                    b=pop(&ps);
+            else if (strcmp(input, "+") == 0) {
                 a=pop(&ps); b=pop(&ps);
-                    if (strcmp(input, "+") == 0) {
+                result = a * b;
-                        result = a + b;
+                push(result, &ps);
-                    }
+
             // /
-                    else if (strcmp(input, "-") == 0)
+            else if (strcmp(input, "+") == 0) {
-                        result = b - a;
+                a=pop(&ps); b=pop(&ps);
 
-                    else if (strcmp(input, "*") == 0)
+                if (a == 0) {
-                        result = a * b;
+                    fprintf(stderr, "Error: Division by zero!\n");
                     exit(EXIT_FAILURE);
-                    else if (strcmp(input, "/") == 0) {
+
-                        if (a == 0) {
+                else result = b / a;
-                            fprintf(stderr, "Error: Division by zero!\n");
+
-                            exit(EXIT_FAILURE);
+                push(result, &ps);
-                        }
+
-                        else result = b / a;
+        }
-                    }
+        // Detect invalid input
         else {
-                    else {
+            fprintf(stderr, "Error: Invalid input!\n");
-                        fprintf(stderr, "Error: Invalid input!\n");
+            exit(EXIT_FAILURE);
-                        exit(EXIT_FAILURE);
+
-                    }
+
 
-                    push(result, &ps);
+    // Returns error when no arguments are entered
     if (count == 0) {
         fprintf(stderr, "Error: No arguments!\n");
         exit(EXIT_FAILURE);
     }
 
-    //returns error when no arguments are entered
+
     // If the last character isn't "p", the program print the result clasically
     if (strcmp(input, "p") != 0) {
         printresult = pop(&ps);
         printf("%lld\n", printresult);
     }
 
-    //if the last character isn't "p", the program print the result clasically
+
 }
 
 
 
 void push(long long int x, STACK *ps)
 {
     if (ps->top == STACKSIZE-1){
         fprintf(stderr, "Error: Stack overflow!\n");
         exit(EXIT_FAILURE);
     } else
         ps->items[++(ps->top)] = x;
-    if(ps->top == STACKSIZE-1){
+
     return;
 }
 
 
 
 int pop(STACK *ps)
 {
     if (ps->top == 0) {
         fprintf(stderr, "Error: Stack underflow!\n");
         exit(EXIT_FAILURE);
     }
-    if(ps->top == 0) {
+
         return(ps->items[(ps->top)--]);
 }
 
 
 
 bool ispositivedigit(char* input)
 {
     // cycle which determines if each character from input is a number or not
-int ispositivedigit(char* input)
+
         if (isdigit(input[i]) == 0) {}
-    //must be initialized to 0 after each cycle
+            return false;
-    int alldigits = 0;
+
     }
-    //cycle which determines if each character from input is a number or not
+
     return true;
-        if (isdigit(input[i]) == 0)
+
-            alldigits = 1; //set alldigits to 1 if the character isn't a number
+
-            return 0;
+
 
-    return 1;
+bool isnegativedigit(char* input)
 {
     if (strlen(input) > 1 && strncmp(input, "-", 1) == 0) {
         for (unsigned int i = 1; i < strlen(input); i++) {
-int isnegativedigit(char* input)
+
                 return false;  // if a character different from number appears, function returns false
-    if (strncmp(input,"-",1) == 0) {
+
-        for (unsigned int i=1; i<strlen(input); i++) {
+
     }
-                return 0; //if a character different from number appears, function returns 0
+
         return false;  // if the firts character isn't "-", function returns false
 
     return true;  // it is a negative number
 }
-        return 0; //if the firts character isn't "-", function returns 0
+
 
-    return 1; //it is a negative number
+
 bool isoperator(char* input)
 {
     if (strlen(input) != 1) return false;  // only one-char operators are allowed
-void printtop(STACK *ps) //bonus
+
     if (strncmp(input, "+", 1) == 0) return true;
-    //not empty stuck
+    if (strncmp(input, "-", 1) == 0) return true;
     if (strncmp(input, "*", 1) == 0) return true;
     if (strncmp(input, "/", 1) == 0) return true;
-    //empty stack
+    if (strncmp(input, "p", 1) == 0) return true;
 
     return false;
 }
 
 
 
 void printtop(STACK *ps)  // bonus
 {
     // not empty stuck
     if (ps->top != 0)
         printf("%lld \n", ps->items[ps->top]);
     // empty stack
     else {
         fprintf(stderr, "Error: Attempt to call for an empty stack!\n");
         exit(EXIT_FAILURE);
     }
 }