Write code to efficiently evaluate given postfix expression.

evaluate_exp.c

// Write code to efficiently evaluate given postfix expression.
int evaluate_exp(char exp[], stck * st) {
    int index = 0, x, y;
    char ch;
    while (exp[index] != '\0') {
        ch = exp[index];
        if (ch >= '0' && ch <= '9') {
            push(ch - '0', st);
        }
        else {
            x = get_peek(*st);
            pop(st);
            y = get_peek(*st);
            pop(st);

            if (ch == '+') push(y + x, st);
            else if (ch == '-') push(y - x, st);
            else if (ch == '*') push(y * x, st);
            else if (ch == '/') push(y / x, st);
        }
        index++;
    }
    return get_peek(*st);
}