Read a postfix expression from the given input file, and evaluate the value of the postfix expression using stack ADT.
1. Input
Obtain a postfix expression from the given input file (expr_input.txt). The expression ends with #. A detailed specification of operators and operands is provided below.
• Available operators: +, -, *, /, and %
• Operands: single-digit numbers (1, 2, 3, 4, 5, 6, 7, 8, and 9)
• Conditions:
• The expression should be no more than 100 characters.
• The delimiter for the end of the expression is ‘#‘.
• No exception handling is required for checking whether the input file exists.
2. Data structure
struct Stack {
char *key;
int top;
int max_stack_size;
};
3. Evaluation algorithm
• Iteratively obtain tokens until you meet the end of an expression.
• There are two rules for popping and pushing the operands from/to the stack:
• When you meet an operand (number), push it onto the stack.
• When you meet an operator, pop two operands from the stack and perform the operation, and push the result back to the stack.
4. Program description
• name: p6.c
• input: a postfix expression in a file
• output: evaluation result in the standard output
Submit to the gitlab your code. ( ~2020/5/21 23:59 )
