static String postfix(String infix) throws Exception {
int error = 0;
int len = infix.length();
Stack<Character> sns = new Stack<Character>();
StringBuilder postfix = new StringBuilder();
int a = 0;
int b = -1;
int parleft = 0;
int parright = 0;
for (int i = 0; i < len; i++) {
char ch = infix.charAt(i);
if (ch == '(') parleft += 1;
if (ch == ')') parright += 1;
// unary를 ~로 바꿔줌
if (ch == '-') {
if (i == 0) ch = '~';
else {
char t = infix.charAt(i - 1);
if (t == '+' || t == '-' || t == '*' || t == '/' || t == '%' || t == '(') ch = '~';
}
}
// postfix로 변환
if ('0' <= ch && ch <= '9') {
if (a == 1) postfix.append(ch);
else {
postfix.append(" ");
postfix.append(ch);
}
a = 1;
b++;
} else if (ch == '+' || ch == '-' || ch == '(' || ch == '*' || ch == '^' || ch == '/'
|| ch == '%' || ch == '~') {
if (ch == '(') {
if (a == 1) throw new Exception();
b = -1;
}
if (a == 0 && ch != '~' && ch != '(') error = 1;
if (sns.isEmpty()) {
sns.push(ch);
} else {
if (ch == '(' || ch == '~' || ch == '^') sns.push(ch);
if (ch != '(' && ch != ')' && ch != '^' && ch != '~') {
while (sns.isEmpty() == false
&& Priority.priority(sns.peek()) >= Priority.priority(ch)) {
postfix.append(" ");
postfix.append(sns.pop());
}
sns.push(ch);
}
}
a = 0;
b++;
} else if (ch == ')') {
if (b == 0) error = 1;
while (sns.peek() != '(') {
postfix.append(" ");
postfix.append(sns.pop());
if (sns.isEmpty()) error = 1;
}
sns.pop();
}
// 다른 연산자 때 ERROR 출력
else {
error = 1;
break;
}
}
while (sns.isEmpty() == false) {
char f**k = sns.pop();
if (f**k == '(') continue;
postfix.append(" ");
postfix.append(f**k);
}
if (parleft != parright) error = 1;
if (error == 1) throw new Exception();
return postfix.toString();
}
