import java.util.Scanner;
import java.util.Stack;
class Postfix2 {
public static void postfix2(String str)
{
String s[] = str.split("");
Stack <String>st = new Stack<String>();
String result = "";
String num1 = "", num2 = "";
for (int i=s.length; i>0; i--)
{
if (!"+".equals(s[i]) && !"-".equals(s[i]) && !"*".equals(s[i]) && !"/".equals(s[i]))
st.push(s[i]);
else
{
num1 = st.pop();
num2 = st.pop();
result = num1 + num2 + s[i];
st.push(result);
}
}
System.out.println("Result: "+st.pop());
}
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
System.out.println("Enter input string.");
String str = sc.next();
postfix2(str);
}
}
2 Answers
i needs to be equal to (s.length - 1) to account for the fact that the indexes start at zero in the first for loop.
Also, you may want to change the condition to i >= 0 since there will be an index of 0 as well unless you skipped that on purpose.
for (int i=(s.length -1); i>0; i--)
{
1 Comment
John Ciociola
@Ivan yeah I just caught that while fixing a typo, thanks!
In the for loop you are starting to index outside of the length of the array. For example, if the array s = [x,y,z], s.length returns 3, but the last element z has index of 2 since elements are indexed starting from 0.
Try changing this
for (int i=s.length; i>0; i--)
to this:
for (int i=s.length-1; i>=0; i--)
0tolength - 1