import java.util.Queue;
import java.util.Stack;
import java.util.concurrent.ArrayBlockingQueue;
import java.lang.Exception;
public class Solution{
Stack<Integer> numberStack = new Stack();
Stack<Character> operatorStack = new Stack();
//assuming op1 is in operator stack and op2 is to be inserted
public boolean hasPrecedence(char op1, char op2){
if (op2 == '/' && op1 != '/'){
return true;
}
if (op2 == '*' && (op1 == '+' || op1 == '-')){
return true;
}
return false;
}
// -1 means invalid
// 0 means number
// 1 means an operator
public int validate(char operand){
booleanStack<Integer> isNumbernumberStack = false;
ifnew (Character.isDigitStack(operand)){
isNumber = true;
}
boolean isOperator = false;
if (operand != '/' || operand !='*' || operand !='+' || operand != '-'){;
Stack<Character> isOperatoroperatorStack = true;
}
if (!(isNumber || isOperator)){
return -1;
}
ifnew Stack(isNumber){
return 0;
};
//assuming op1 is in operator stack and op2 is to be inserted
public boolean hasPrecedence(char op1, char op2){
if (isOperatorop2 == '/' && op1 != '/'){
return 1;true;
}
if (op2 == '*' && (op1 == '+' || op1 == '-')){
return true;
}
return false;
}
return// -1;
}
private void performOperation(){
if(operatorStack.empty()1 ||means numberStack.empty()){invalid
// 0 means return;number
}
// 1 means charan operator = operatorStack.pop();
if(numberStack.size() < 2){
return;
}
int num2 = numberStack.pop();
public int num1 = numberStack.popvalidate();
int result = 0;
char switch(operatoroperand){
case '/':boolean resultisNumber = num1/num2;false;
if numberStack(Character.pushisDigit(resultoperand);){
break;
case '+': resultisNumber = num1+num2;
true; numberStack.push(result);
break;}
case '*':boolean resultisOperator = num1*num2;false;
if numberStack.push(result);
operand != '/' break;
|| operand !='*' || operand !='+' || operand case!= '-': result = num1-num2;
numberStack.push(result);{
isOperator = break;true;
} }
if (!(isNumber || isOperator)){
return -1;
}
private int calculate(String exp) throws Exception if (isNumber){
return 0;
if (exp == null ||}
exp.trim().length() == 0
if (isOperator){
throw new Exception("Null or emptyreturn expression1;
"); }
return -1;
}
char[] operArray = exp.toCharArray();
StringBuffer numberBuffer = new StringBuffer();
char operand = '\0';
private forvoid performOperation(int i=0; i < operArray.length ; i++){
operand = operArray[i];
if (CharacteroperatorStack.isWhitespaceempty(operand) || numberStack.empty()){
continue;return;
}
int opVal = -1;
char opValoperator = validateoperatorStack.pop(operand);
if (opValnumberStack.size() ==< -12){
throw new Exception("Invalid inputs ");return;
}
int num2 = numberStack.pop();
int num1 = numberStack.pop();
int result = 0;
switch(operator){
case '/': result = num1/num2;
numberStack.push(result);
break;
case '+': result = num1+num2;
numberStack.push(result);
break;
case '*': result = num1*num2;
numberStack.push(result);
break;
case '-': result = num1-num2;
numberStack.push(result);
break;
}
}
private int calculate(String exp) throws Exception{
//current char is number
if (exp == null if|| exp.trim(opVal).length() == 0 ){
numberBuffer.append(operand);
throw new Exception("Null or empty expression continue;");
}
char[] operArray = exp.toCharArray();
StringBuffer numberBuffer = new StringBuffer();
if (opVal == 1){
numberStack.push(Integer.parseInt(numberBuffer.toString()));
numberBuffer = new StringBuffer();
char operand = '\0';
for (int i=0; i < operArray.length ; i++){
operand = operArray[i];
if (Character.isWhitespace(operand)){
continue;
}
int opVal = -1;
opVal = validate(operand);
if (opVal == -1){
throw new Exception("Invalid inputs ");
}
//current char is number
if (opVal == 0){
numberBuffer.append(operand);
continue;
}
if (opVal == 1){
numberStack.push(Integer.parseInt(numberBuffer.toString()));
numberBuffer = new StringBuffer();
if (!operatorStack.empty()){
if(!hasPrecedence(operatorStack.peek(), operand)){
performOperation();
}
}
operatorStack.push(operand);
}
operatorStack.push(operand);
}
}
numberStack.push(Integer.parseInt(numberBuffer.toString()));
while(!operatorStack.isEmpty()){
performOperation();
}
return numberStack.pop();
}
return numberStack.pop();
}
public static void main(String []args) throws Exception{
Solution expparser = new Solution();
int result = expparser.calculate("3+2*2");
System.out.println("result is " + result);
result = expparser.calculate(" 3/2 ");
System.out.println("result is " + result);
result = expparser.calculate(" 3+5 / 2 ");
System.out.println("result is " + result);
result = expparser.calculate("3+2-2");
System.out.println("result is " + result);
result = expparser.calculate(" 3/2-1 ");
System.out.println("result is " + result);
result = expparser.calculate(" 3/5/2 ");
System.out.println("result is " + result);
result = expparser.calculate("3/5*2");
System.out.println("result is " + result);
result = expparser.calculate("3*5*2");
System.out.println("result is " + result);
result = expparser.calculate(" 3+5+2 ");
System.out.println("result is " + result);
}
}
Became Hot Network Question
import java.util.Queue;
import java.util.Stack;
import java.util.concurrent.ArrayBlockingQueue;
import java.lang.Exception;
public class Solution{
Stack<Integer> numberStack = new Stack();
Stack<Character> operatorStack = new Stack();
//assuming op1 is in operator stack and op2 is to be inserted
public boolean hasPrecedence(char op1, char op2){
if (op2 == '/' && op1 != '/'){
return true;
}
if (op2 == '*' && (op1 == '+' || op1 == '-')){
return true;
}
return false;
}
// -1 means invalid
// 0 means number
// 1 means an operator
public int validate(char operand){
boolean isNumber = false;
if (Character.isDigit(operand)){
isNumber = true;
}
boolean isOperator = false;
if (operand != '/' || operand !='*' || operand !='+' || operand != '-'){
isOperator = true;
}
if (!(isNumber || isOperator)){
return -1;
}
if (isNumber){
return 0;
}
if (isOperator){
return 1;
}
return -1;
}
private void performOperation(){
if(operatorStack.empty() || numberStack.empty()){
return;
}
char operator = operatorStack.pop();
if(numberStack.size() < 2){
return;
}
int num2 = numberStack.pop();
int num1 = numberStack.pop();
int result = 0;
switch(operator){
case '/': result = num1/num2;
numberStack.push(result);
break;
case '+': result = num1+num2;
numberStack.push(result);
break;
case '*': result = num1*num2;
numberStack.push(result);
break;
case '-': result = num1-num2;
numberStack.push(result);
break;
}
}
private int calculate(String exp) throws Exception{
if (exp == null || exp.trim().length() == 0 ){
throw new Exception("Null or empty expression ");
}
char[] operArray = exp.toCharArray();
StringBuffer numberBuffer = new StringBuffer();
char operand = '\0';
for (int i=0; i < operArray.length ; i++){
operand = operArray[i];
if (Character.isWhitespace(operand)){
continue;
}
int opVal = -1;
opVal = validate(operand);
if (opVal == -1){
throw new Exception("Invalid inputs ");
}
//current char is number
if (opVal == 0){
numberBuffer.append(operand);
continue;
}
if (opVal == 1){
numberStack.push(Integer.parseInt(numberBuffer.toString()));
numberBuffer = new StringBuffer();
if (!operatorStack.empty()){
if(!hasPrecedence(operatorStack.peek(), operand)){
performOperation();
}
}
operatorStack.push(operand);
}
}
numberStack.push(Integer.parseInt(numberBuffer.toString()));
while(!operatorStack.isEmpty()){
performOperation();
}
return numberStack.pop();
}
public static void main(String []args) throws Exception{
Solution expparser = new Solution();
int result = expparser.calculate("3+2*2");
System.out.println("result is " + result);
result = expparser.calculate(" 3/2 ");
System.out.println("result is " + result);
result = expparser.calculate(" 3+5 / 2 ");
System.out.println("result is " + result);
result = expparser.calculate("3+2-2");
System.out.println("result is " + result);
result = expparser.calculate(" 3/2-1 ");
System.out.println("result is " + result);
result = expparser.calculate(" 3/5/2 ");
System.out.println("result is " + result);
result = expparser.calculate("3/5*2");
System.out.println("result is " + result);
result = expparser.calculate("3*5*2");
System.out.println("result is " + result);
result = expparser.calculate(" 3+5+2 ");
System.out.println("result is " + result);
}
import java.util.Queue;
import java.util.Stack;
import java.util.concurrent.ArrayBlockingQueue;
import java.lang.Exception;
public class Solution{
Stack<Integer> numberStack = new Stack();
Stack<Character> operatorStack = new Stack();
//assuming op1 is in operator stack and op2 is to be inserted
public boolean hasPrecedence(char op1, char op2){
if (op2 == '/' && op1 != '/'){
return true;
}
if (op2 == '*' && (op1 == '+' || op1 == '-')){
return true;
}
return false;
}
// -1 means invalid
// 0 means number
// 1 means an operator
public int validate(char operand){
boolean isNumber = false;
if (Character.isDigit(operand)){
isNumber = true;
}
boolean isOperator = false;
if (operand != '/' || operand !='*' || operand !='+' || operand != '-'){
isOperator = true;
}
if (!(isNumber || isOperator)){
return -1;
}
if (isNumber){
return 0;
}
if (isOperator){
return 1;
}
return -1;
}
private void performOperation(){
if(operatorStack.empty() || numberStack.empty()){
return;
}
char operator = operatorStack.pop();
if(numberStack.size() < 2){
return;
}
int num2 = numberStack.pop();
int num1 = numberStack.pop();
int result = 0;
switch(operator){
case '/': result = num1/num2;
numberStack.push(result);
break;
case '+': result = num1+num2;
numberStack.push(result);
break;
case '*': result = num1*num2;
numberStack.push(result);
break;
case '-': result = num1-num2;
numberStack.push(result);
break;
}
}
private int calculate(String exp) throws Exception{
if (exp == null || exp.trim().length() == 0 ){
throw new Exception("Null or empty expression ");
}
char[] operArray = exp.toCharArray();
StringBuffer numberBuffer = new StringBuffer();
char operand = '\0';
for (int i=0; i < operArray.length ; i++){
operand = operArray[i];
if (Character.isWhitespace(operand)){
continue;
}
int opVal = -1;
opVal = validate(operand);
if (opVal == -1){
throw new Exception("Invalid inputs ");
}
//current char is number
if (opVal == 0){
numberBuffer.append(operand);
continue;
}
if (opVal == 1){
numberStack.push(Integer.parseInt(numberBuffer.toString()));
numberBuffer = new StringBuffer();
if (!operatorStack.empty()){
if(!hasPrecedence(operatorStack.peek(), operand)){
performOperation();
}
}
operatorStack.push(operand);
}
}
numberStack.push(Integer.parseInt(numberBuffer.toString()));
while(!operatorStack.isEmpty()){
performOperation();
}
return numberStack.pop();
}
public static void main(String []args) throws Exception{
Solution expparser = new Solution();
int result = expparser.calculate("3+2*2");
System.out.println("result is " + result);
result = expparser.calculate(" 3/2 ");
System.out.println("result is " + result);
result = expparser.calculate(" 3+5 / 2 ");
System.out.println("result is " + result);
result = expparser.calculate("3+2-2");
System.out.println("result is " + result);
result = expparser.calculate(" 3/2-1 ");
System.out.println("result is " + result);
result = expparser.calculate(" 3/5/2 ");
System.out.println("result is " + result);
result = expparser.calculate("3/5*2");
System.out.println("result is " + result);
result = expparser.calculate("3*5*2");
System.out.println("result is " + result);
result = expparser.calculate(" 3+5+2 ");
System.out.println("result is " + result);
}
}
Input: "3+2*2" Output: 7 Example 2:
Input: "3+2*2"
Output: 7
Input: " 3/2 " Output: 1 Example 3Example 2:
Input: " 3/2 "
Output: 1
Input: " 3+5 / 2 " OutputExample 3: 5
Input: " 3+5 / 2 "
Output: 5
}
Input: "3+2*2" Output: 7 Example 2:
Input: " 3/2 " Output: 1 Example 3:
Input: " 3+5 / 2 " Output: 5
}
Input: "3+2*2"
Output: 7
Example 2:
Input: " 3/2 "
Output: 1
Example 3:
Input: " 3+5 / 2 "
Output: 5
leet code calculator II code
This is a problem that is asked on leet code for a simple calculator. The problem is stated as follows -
Implement a basic calculator to evaluate a simple expression string.
The expression string contains only non-negative integers, +, -, *, / operators and empty spaces . The integer division should truncate toward zero.
Example 1:
Input: "3+2*2" Output: 7 Example 2:
Input: " 3/2 " Output: 1 Example 3:
Input: " 3+5 / 2 " Output: 5
Note: You may assume that the given expression is always valid. Do not use the eval built-in library function.
This is the code I wrote in a short span of time, I did not design it for more complicated cases -
import java.util.Queue;
import java.util.Stack;
import java.util.concurrent.ArrayBlockingQueue;
import java.lang.Exception;
public class Solution{
Stack<Integer> numberStack = new Stack();
Stack<Character> operatorStack = new Stack();
//assuming op1 is in operator stack and op2 is to be inserted
public boolean hasPrecedence(char op1, char op2){
if (op2 == '/' && op1 != '/'){
return true;
}
if (op2 == '*' && (op1 == '+' || op1 == '-')){
return true;
}
return false;
}
// -1 means invalid
// 0 means number
// 1 means an operator
public int validate(char operand){
boolean isNumber = false;
if (Character.isDigit(operand)){
isNumber = true;
}
boolean isOperator = false;
if (operand != '/' || operand !='*' || operand !='+' || operand != '-'){
isOperator = true;
}
if (!(isNumber || isOperator)){
return -1;
}
if (isNumber){
return 0;
}
if (isOperator){
return 1;
}
return -1;
}
private void performOperation(){
if(operatorStack.empty() || numberStack.empty()){
return;
}
char operator = operatorStack.pop();
if(numberStack.size() < 2){
return;
}
int num2 = numberStack.pop();
int num1 = numberStack.pop();
int result = 0;
switch(operator){
case '/': result = num1/num2;
numberStack.push(result);
break;
case '+': result = num1+num2;
numberStack.push(result);
break;
case '*': result = num1*num2;
numberStack.push(result);
break;
case '-': result = num1-num2;
numberStack.push(result);
break;
}
}
private int calculate(String exp) throws Exception{
if (exp == null || exp.trim().length() == 0 ){
throw new Exception("Null or empty expression ");
}
char[] operArray = exp.toCharArray();
StringBuffer numberBuffer = new StringBuffer();
char operand = '\0';
for (int i=0; i < operArray.length ; i++){
operand = operArray[i];
if (Character.isWhitespace(operand)){
continue;
}
int opVal = -1;
opVal = validate(operand);
if (opVal == -1){
throw new Exception("Invalid inputs ");
}
//current char is number
if (opVal == 0){
numberBuffer.append(operand);
continue;
}
if (opVal == 1){
numberStack.push(Integer.parseInt(numberBuffer.toString()));
numberBuffer = new StringBuffer();
if (!operatorStack.empty()){
if(!hasPrecedence(operatorStack.peek(), operand)){
performOperation();
}
}
operatorStack.push(operand);
}
}
numberStack.push(Integer.parseInt(numberBuffer.toString()));
while(!operatorStack.isEmpty()){
performOperation();
}
return numberStack.pop();
}
public static void main(String []args) throws Exception{
Solution expparser = new Solution();
int result = expparser.calculate("3+2*2");
System.out.println("result is " + result);
result = expparser.calculate(" 3/2 ");
System.out.println("result is " + result);
result = expparser.calculate(" 3+5 / 2 ");
System.out.println("result is " + result);
result = expparser.calculate("3+2-2");
System.out.println("result is " + result);
result = expparser.calculate(" 3/2-1 ");
System.out.println("result is " + result);
result = expparser.calculate(" 3/5/2 ");
System.out.println("result is " + result);
result = expparser.calculate("3/5*2");
System.out.println("result is " + result);
result = expparser.calculate("3*5*2");
System.out.println("result is " + result);
result = expparser.calculate(" 3+5+2 ");
System.out.println("result is " + result);
}
}
Considering there are no negative numbers in the expression, this code works fine and the test cases have all passed. How can I improve this code?
lang-java