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| private static final char PLUS = '+';
private static final char MINUS = '-';
private static final char MULTIPLICATION = '*';
public long solution(String expression) {
char[] chars = expression.toCharArray();
Object[] numberAndOperator = getNumbersAndOperatorSet(chars);
List<Long> numberList = (List<Long>) numberAndOperator[0];
List<Character> operatorList = (List<Character>) numberAndOperator[1];
char[] operators = getExpressionIncludeOperators(operatorList);
List<String> operatorSetList = getOperatorSetList(operators);
return getMax(numberList, operatorList, operatorSetList);
}
private Object[] getNumbersAndOperatorSet(char[] expression) {
List<Long> numberList = new ArrayList<>();
List<Character> operatorList = new ArrayList<>();
StringBuilder sb = new StringBuilder();
for (char c : expression) {
switch (c) {
case PLUS:
case MINUS:
case MULTIPLICATION:
numberList.add(Long.valueOf(sb.toString()));
operatorList.add(c);
sb.setLength(0);
break;
default:
sb.append(c);
break;
}
}
numberList.add(Long.valueOf(sb.toString()));
return new Object[] {numberList, operatorList};
}
private char[] getExpressionIncludeOperators(List<Character> operatorList) {
Set<Character> set = new HashSet<>();
List<Character> list = new ArrayList<>();
for (char c : operatorList) {
if (set.add(c)) {
list.add(c);
}
}
char[] operators = new char[list.size()];
int i = 0;
for (char c : list) {
operators[i++] = c;
}
return operators;
}
private List<String> getOperatorSetList(char[] chars) {
List<String> operatorSetList = new ArrayList<>();
Set<String> set = new HashSet<>();
for (int i = 1; i <= chars.length; i++) {
perm(chars, 0, i, operatorSetList, set);
}
return operatorSetList;
}
private void perm(char[] array, int depth, int length, List<String> operatorList, Set<String> set) {
if (depth == length) {
StringBuilder sb = new StringBuilder();
for (char c : array) {
sb.append(c);
}
if (set.add(sb.toString())) {
operatorList.add(sb.toString());
}
return;
}
for (int i = depth; i < array.length; i++) {
swap(array, i, depth);
perm(array, depth + 1, length, operatorList, set);
swap(array, i, depth);
}
}
private void swap(char[] arrary, int i, int j) {
char temp = arrary[i];
arrary[i] = arrary[j];
arrary[j] = temp;
}
private Long getMax(List<Long> numberList, List<Character> operatorList, List<String> operatorSetList) {
long max = 0;
for (String operatorSet : operatorSetList) {
char[] operators = operatorSet.toCharArray();
LinkedList<Long> numberQueue = new LinkedList<>(numberList);
LinkedList<Character> operatorQueue = new LinkedList<>(operatorList);
for (char operatorToCalculate : operators) {
Stack<Long> numberStack = new Stack<>();
Stack<Character> operatorStack = new Stack<>();
long first = numberQueue.poll();
numberStack.push(first);
numberQueue.offer(first);
Stack[] stacks = new Stack[] {numberStack, operatorStack};
LinkedList[] queues = new LinkedList[] {numberQueue, operatorQueue};
calculatePriority(stacks, queues, operatorToCalculate);
}
max = (max > Math.abs(numberQueue.peek())) ? max : Math.abs(numberQueue.poll());
}
return max;
}
private void calculatePriority(Stack[] staks, LinkedList[] queues, char operatorToCalculate) {
Stack<Long> numberStack = staks[0];
Stack<Character> operatorStack = staks[1];
LinkedList<Long> numberQueue = queues[0];
LinkedList<Character> operatorQueue = queues[1];
int limit = operatorQueue.size();
for (int i = 0; i < limit; i++) {
long currentNumber = numberQueue.poll();
numberStack.push(currentNumber);
Character currentOperator = operatorQueue.poll();
operatorStack.push(currentOperator);
if (operatorStack.peek() == operatorToCalculate) {
long n1 = numberStack.pop();
long n2 = numberStack.pop();
char op = operatorStack.pop();
long sum = sum(n2, n1, op);
numberStack.push(sum);
numberQueue.pollLast();
numberQueue.offer(sum);
} else {
numberQueue.offer(currentNumber);
operatorQueue.offer(currentOperator);
}
}
}
private Long sum(long n2, long n1, char op) {
long sum = 0;
switch (op) {
case '*' :
sum = n2 * n1;
break;
case '+' :
sum = n2 + n1;
break;
case '-' :
sum = n2 - n1;
break;
}
return sum;
}
|