infix to postfix - stack

Author: hemangsk

Data Structures/stack/baseConverter.py

@@ -29,4 +29,4 @@ def baseConvert(num, base):
 
     return result
 
-print(baseConvert(25,2))
+print(baseConvert(2,2))

Data Structures/stack/infix2postfix.py

@@ -0,0 +1,58 @@
+class Stack:
+    """docstring for stack."""
+    def __init__(self):
+        self.stack = []
+    def push(self, item):
+        self.stack.append(item)
+    def pop(self):
+        return self.stack.pop()
+    def peek(self):
+        return self.stack[self.size()-1]
+    def isEmpty(self):
+        return self.stack == []
+    def size(self):
+        return len(self.stack)
+
+def infix2postFix(string):
+    prec = {}
+    prec["*"] = 3
+    prec["/"] = 3
+    prec["+"] = 3
+    prec["-"] = 3
+    prec["("] = 1
+
+    s = Stack()
+    expression = string.split(' ')
+    result = ""
+
+    for x in expression:
+        if x == "(":
+            s.push(x)
+
+        elif x == ")":
+            item = s.pop()
+            while(item != "("):
+                result += item
+                item = s.pop()
+
+        elif x in "1234567890" or x in "abcdefghijklmnopqrstuvwxyz":
+            result +=x
+
+        elif x in "*/-+" and s.size() != 0:
+            if s.peek() in "*/+-":
+                while(prec[s.peek()] >= prec[x] ):
+                    result+=s.pop()
+                s.push(x)
+            s.push(x)
+
+        elif x in "*/-+":
+            s.push(x)
+
+    leftStack = s.size()
+
+    while(leftStack > 0):
+        result+=s.pop()
+        leftStack -= 1
+    return result
+
+print(infix2postFix("9 + 3"))

Data Structures/stack/reversedNumbers.py

@@ -0,0 +1,57 @@
+
+class Stack:
+    def __init__(self):
+        self.stack = []
+    def push(self, item):
+        self.stack.append(item)
+    def pop(self):
+        return self.stack.pop()
+    def isEmpty(self):
+        return self.stack == []
+    def size(self):
+        return len(self.stack)
+
+n = int(input())
+while (n > 0):
+    n = n - 1
+    x = str(input())
+    a, b = x.split(' ')
+    aS = Stack()
+    bS = Stack()
+    for x in a:
+        aS.push(int(x))
+    for y in b:
+        bS.push(int(y))
+    string1 = ""
+    string2 = ""
+    while (aS.isEmpty() == False):
+        string1 += str(aS.pop())
+    while (bS.isEmpty() == False):
+        string2 += str(bS.pop())
+
+    # print("String1" + string1)
+    digit1 = int(string1)
+    digit2 = int(string2)
+
+    sum = digit1 + digit2
+
+    sS = Stack()
+    sumString = str(sum)
+
+    for x in sumString:
+        sS.push(int(x))
+
+    result = ""
+
+    length = sS.size()
+
+    while (length > 0):
+        length = length - 1
+        item = sS.pop()
+        if (item != 0):
+            sS.push(item)
+            break
+
+    while (sS.isEmpty() == False):
+        result += str(sS.pop())
+    print(result)

Data Structures/stack/reversedString2.py

@@ -0,0 +1,14 @@
+n = int(input())
+while(n > 0):
+    n = n-1
+    a = raw_input()
+#    print(a)
+    x,y = a.split(' ')
+    x = x[::-1]
+    y = y[::-1]
+    res = int(x) + int(y)
+    res = str(res)
+    while (res[len(res)-1: len(res)] == '0') and len(res) > 0:
+        res = res[:len(res)-1]
+    res = res[::-1]
+    print(res)