RPN with C language - c

Question

I have problem with this code, It works fine with small values but with big values it crash.
for Example.
input:
1+2+3
output:
Expression:
1+2+3
Reverse Polish Notation:
12+3+
Result:
6
but with this example it crash
input:
100+2*100/50
output:
runtime-error
This code is converting infix to postfix and this calculate the RPN.
// C program to convert infix expression to postfix
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
struct Stack
{
int top;
unsigned capacity;
int* array;
};
struct Stack* createStack(unsigned capacity)
{
struct Stack* stack = (struct Stack*)
malloc(sizeof(struct Stack));
if (!stack)
return NULL;
stack->top = -1;
stack->capacity = capacity;
stack->array = (int*)malloc(stack->capacity *
sizeof(int));
return stack;
}
int isEmpty(struct Stack* stack)
{
return stack->top == -1;
}
char peek(struct Stack* stack)
{
return stack->array[stack->top];
}
char pop(struct Stack* stack)
{
if (!isEmpty(stack))
return stack->array[stack->top--];
return '$';
}
void push(struct Stack* stack, char op)
{
stack->array[++stack->top] = op;
}
int isOperand(char ch)
{
return (ch >= '0' && ch <= '9');
}
int Prec(char ch)
{
switch (ch)
{
case '+':
case '-':
return 1;
case '*':
case '/':
return 2;
case '^':
return 3;
}
return -1;
}
int infixToPostfix(char* exp)
{
int i, k;
struct Stack* stack = createStack(strlen(exp));
if (!stack)
return -1;
for (i = 0, k = -1; exp[i]; ++i)
{
if (isOperand(exp[i]))
exp[++k] = exp[i];
else if (exp[i] == '(')
push(stack, exp[i]);
else if (exp[i] == ')')
{
while (!isEmpty(stack) && peek(stack) != '(')
exp[++k] = pop(stack);
if (!isEmpty(stack) && peek(stack) != '(')
return -1;
else
pop(stack);
}
else
{
while (!isEmpty(stack) &&
Prec(exp[i]) <= Prec(peek(stack)))
exp[++k] = pop(stack);
push(stack, exp[i]);
}
}
while (!isEmpty(stack))
exp[++k] = pop(stack);
exp[++k] = '\0';
printf("Reverse Polish Notation:\n");
char str[10];
strcpy(str, exp);
for (int i = 0; str[i]; i++)
{
printf("%c ", str[i]);
}
printf("\n");
}
int evaluatePostfix(char* exp)
{
struct Stack* stack = createStack(strlen(exp));
int i;
if (!stack) return -1;
for (i = 0; exp[i]; ++i)
{
if (isdigit(exp[i]))
push(stack, exp[i] - '0');
else
{
int val1 = pop(stack);
int val2 = pop(stack);
switch (exp[i])
{
case '+': push(stack, val2 + val1); break;
case '-': push(stack, val2 - val1); break;
case '*': push(stack, val2 * val1); break;
case '/': push(stack, val2 / val1); break;
}
}
}
return pop(stack);
}
int main()
{
//char exp[] = "1+2+3";
char exp[10];
scanf("%14s", exp);
printf("Expression:\n%s\n", exp);
infixToPostfix(exp);
printf("Result:\n%d", evaluatePostfix(exp));
return 0;
}