Algorithm
Problem link- https://www.spoj.com/problems/ONP/
ONP - Transform the Expression
Transform the algebraic expression with brackets into RPN form (Reverse Polish Notation). Two-argument operators: +, -, *, /, ^ (priority from the lowest to the highest), brackets ( ). Operands: only letters: a,b,...,z. Assume that there is only one RPN form (no expressions like a*b*c).
Input
t [the number of expressions <= 100] expression [length <= 400] [other expressions]
Text grouped in [ ] does not appear in the input file.
Output
The expressions in RPN form, one per line.
Example
Input: 3 (a+(b*c)) ((a+b)*(z+x)) ((a+t)*((b+(a+c))^(c+d))) Output: abc*+ ab+zx+* at+bac++cd+^*
Code Examples
#1 Code Example with Java Programming
Code -
Java Programming
import java.io.*;
import java.util.*;
import java.util.Stack;
class Immutable{
public static void main(String[] args){
InputReader in = new InputReader(System.in);
OutputWriter out = new OutputWriter(System.out);
int t = in.readInt();
while(t-- > 0){
String input = in.readString();
Stack<Character> stack = new Stack < >();
for(int i = 0;i < input.length(); i ++){
if(input.charAt(i) >= 97 && input.charAt(i) <=122){
out.print(input.charAt(i));
}else if(input.charAt(i)==')'){
out.print(stack.pop());
stack.pop();
}else{
stack.push(input.charAt(i));
}
}
out.printLine();
}
out.flush();
out.close();
}
}
class InputReader
{
private InputStream stream;
private byte[] buf = new byte[1024];
private int curChar;
private int numChars;
private SpaceCharFilter filter;
public InputReader(InputStream stream)
{
this.stream = stream;
}
public int read()
{
if (numChars == -1)
throw new InputMismatchException();
if (curChar >= numChars)
{
curChar = 0;
try
{
numChars = stream.read(buf);
} catch (IOException e)
{
throw new InputMismatchException();
}
if (numChars <= 0)
return -1;
}
return buf[curChar++];
}
public int readInt()
{
int c = read();
while (isSpaceChar(c))
c = read();
int sgn = 1;
if (c == '-')
{
sgn = -1;
c = read();
}
int res = 0;
do
{
if (c < '0' || c > '9')
throw new InputMismatchException();
res *= 10;
res += c - '0';
c = read();
} while (!isSpaceChar(c));
return res * sgn;
}
public String readString()
{
int c = read();
while (isSpaceChar(c))
c = read();
StringBuilder res = new StringBuilder();
do
{
res.appendCodePoint(c);
c = read();
} while (!isSpaceChar(c));
return res.toString();
}
public double readDouble() {
int c = read();
while (isSpaceChar(c))
c = read();
int sgn = 1;
if (c == '-') {
sgn = -1;
c = read();
}
double res = 0;
while (!isSpaceChar(c) && c != '.') {
if (c == 'e' || c == 'E')
return res * Math.pow(10, readInt());
if (c < '0' || c > '9')
throw new InputMismatchException();
res *= 10;
res += c - '0';
c = read();
}
if (c == '.') {
c = read();
double m = 1;
while (!isSpaceChar(c)) {
if (c == 'e' || c == 'E')
return res * Math.pow(10, readInt());
if (c < '0' || c > '9')
throw new InputMismatchException();
m /= 10;
res += (c - '0') * m;
c = read();
}
}
return res * sgn;
}
public long readLong() {
int c = read();
while (isSpaceChar(c))
c = read();
int sgn = 1;
if (c == '-') {
sgn = -1;
c = read();
}
long res = 0;
do {
if (c < '0' || c > '9')
throw new InputMismatchException();
res *= 10;
res += c - '0';
c = read();
} while (!isSpaceChar(c));
return res * sgn;
}
public boolean isSpaceChar(int c)
{
if (filter != null)
return filter.isSpaceChar(c);
return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
}
public String next()
{
return readString();
}
public interface SpaceCharFilter
{
public boolean isSpaceChar(int ch);
}
}
class OutputWriter
{
private PrintWriter writer;
public OutputWriter(OutputStream outputStream)
{
writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
}
public OutputWriter(Writer writer)
{
this.writer = new PrintWriter(writer);
}
public void print(Object... objects)
{
for (int i = 0; i < objects.length; i++)
{
if (i != 0)
writer.print(' ');
writer.print(objects[i]);
}
}
public void printLine(Object... objects)
{
print(objects);
writer.println();
}
public void close()
{
writer.close();
}
public void flush()
{
writer.flush();
}
}Input
3
(a+(b*c))
((a+b)*(z+x))
((a+t)*((b+(a+c))^(c+d)))
(a+(b*c))
((a+b)*(z+x))
((a+t)*((b+(a+c))^(c+d)))
Output
abc*+
ab+zx+*
at+bac++cd+^*
ab+zx+*
at+bac++cd+^*
#2 Code Example with C++ Programming
Code -
C++ Programming
#include<bits/stdc++.h>
using namespace std;
char str[405];
int main()
{
int tc;
scanf("%d",&tc);
while(tc--){
scanf("%s",str);
stack<char>st;
int len = strlen(str);
for(int i=0; i<len; i++){
if(str[i]=='(')
st.push(str[i]);
else if(str[i]==')'){
char ch = st.top();
st.pop();
st.pop();
printf("%c",ch);
}
else if(isalpha(str[i])) printf("%c",str[i]);
else st.push(str[i]);
}
printf("\n");
}
return 0;
}Input
3
(a+(b*c))
((a+b)*(z+x))
((a+t)*((b+(a+c))^(c+d)))
(a+(b*c))
((a+b)*(z+x))
((a+t)*((b+(a+c))^(c+d)))
Output
abc*+
ab+zx+*
at+bac++cd+^*
ab+zx+*
at+bac++cd+^*
Demonstration
SPOJ Solution-Transform the Expression-Solution in C, C++, Java, Python