Add Chapter 9 exercises

thinkcspy/Chapter-9-Exercises/Python-files/Problem10.py

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+# Runestone.Academy thinkcspy course
+# Chapter 9
+# Problem 10
+
+def count(substr,theStr):
+    # your code here
+    count = 0
+    charCount = 0
+    pos1 = 0
+    pos2 = len(substr)
+    charPos = len(substr)
+    
+    while charCount < len(theStr):
+        if charPos == 1 and substr == theStr[pos1] and (pos2 == len(theStr) or substr != theStr[pos2]):
+            count += 1
+            charCount += 1
+        elif  substr == theStr[pos1:pos2]:
+            count += 1
+            charCount += charPos + 1
+        else:
+            charCount += 1
+            
+
+        pos1 += 1
+        pos2 += 1
+                
+    return count
+
+print(count("e", "treeleee"))

thinkcspy/Chapter-9-Exercises/Python-files/Problem11.py

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+# Runestone.Academy thinkcspy course
+# Chapter 9
+# Problem 11
+
+def remove(substr,theStr):
+    # your code here
+    pos1 = 0
+    pos2 = len(substr)
+    found = False
+    newStr = theStr
+    
+    while pos1 < len(newStr) and not found:
+        currentPos = newStr[pos1:pos2]
+        
+        if substr == currentPos:
+            newStr = newStr[:pos1] + newStr[pos2:]
+            found = True
+        else:
+            pos1 += 1
+            pos2 += 1
+    
+    return newStr
+
+print(remove("e", "tree"))
+print(remove("iss", "Mississippi"))
+print(remove("an", "banana"))
+print(remove("e", "treeeleee"))

thinkcspy/Chapter-9-Exercises/Python-files/Problem12.py

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+# Runestone.Academy thinkcspy course
+# Chapter 9
+# Problem 12
+
+def remove_all(substr,theStr):
+    # your code here
+    pos1 = 0
+    pos2 = len(substr)
+    newStr = theStr
+    
+    while pos1 < len(newStr):
+        currentPos = newStr[pos1:pos2]
+        
+        if substr == currentPos:
+            newStr = newStr[:pos1] + newStr[pos2:]
+        else:
+            pos1 += 1
+            pos2 += 1
+       
+    return newStr
+
+
+print(remove_all("e", "treeeleee"))

thinkcspy/Chapter-9-Exercises/Python-files/Problem14.py

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+# Runestone.Academy thinkcspy course
+# Chapter 9
+# Problem 14
+
+# Your code here
+import turtle
+
+def createLSystem(numIters,axiom):
+    startString = axiom
+    endString = ""
+    for i in range(numIters):
+        endString = processString(startString)
+        startString = endString
+
+    return endString
+
+def processString(oldStr):
+    newstr = ""
+    for ch in oldStr:
+        newstr = newstr + applyRules(ch)
+
+    return newstr
+
+def applyRules(ch):
+    newstr = ""
+    if ch == 'X':
+        newstr = 'X+YF+'   # Rule 1
+    elif ch == 'Y':
+        newstr = '-FX-Y'   # Rule 2
+    else:
+        newstr = ch    # no rules apply so keep the character
+
+    return newstr
+
+def drawLsystem(aTurtle, instructions, angle, distance):
+    for cmd in instructions:
+        if cmd == 'F':
+            aTurtle.forward(distance)
+        elif cmd == 'B':
+            aTurtle.backward(distance)
+        elif cmd == '+':
+            aTurtle.right(angle)
+        elif cmd == '-':
+            aTurtle.left(angle)
+
+def main():
+    inst = createLSystem(10, "FX")   # create the string
+    print(inst)
+    t = turtle.Turtle()            # create the turtle
+    wn = turtle.Screen()
+    wn.tracer(10)
+
+    t.up()
+    t.back(100)
+    t.down()
+    t.speed(0)
+    drawLsystem(t, inst, 90, 5)   # draw the picture
+                                  # angle 90, segment length 5
+    wn.exitonclick()
+
+main()

thinkcspy/Chapter-9-Exercises/Python-files/Problem18.py

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+# Runestone.Academy thinkcspy course
+# Chapter 9
+# Problem 18
+
+import string
+
+def encrypt(msg, code):
+    alpha = string.ascii_lowercase
+    newStr = ""
+    pos = 0
+    msg = msg.lower()
+    
+    for char in msg:
+        if char in alpha:
+            pos = alpha.index(char)
+            newStr += newAlpha[pos]
+        else:
+            newStr += char    # no rules apply so keep the character
+
+    return newStr
+
+newAlpha = "qwertyuiopasdfghjklzxcvbnm"
+
+print(encrypt("Hello World!", newAlpha))

thinkcspy/Chapter-9-Exercises/Python-files/Problem19.py

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+# Runestone.Academy thinkcspy course
+# Chapter 9
+# Problem 19
+
+import string
+
+def decrypt(msg, code):
+    alpha = string.ascii_lowercase
+    newStr = ""
+    pos = 0
+    msg = msg.lower()
+    
+    for char in msg:
+        if char in alpha:
+            pos = newAlpha.index(char)
+            newStr += alpha[pos]
+        else:
+            newStr += char    # no rules apply so keep the character
+
+    return newStr
+
+newAlpha = "qwertyuiopasdfghjklzxcvbnm"
+
+print(decrypt("itssg vgksr!", newAlpha))

thinkcspy/Chapter-9-Exercises/Python-files/Problem21.py

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+# Runestone.Academy thinkcspy course
+# Chapter 9
+# Problem 21
+
+import string
+
+def rot13(mess):
+    # Your code here
+    alpha = string.ascii_lowercase
+    newStr = ""
+    pos = 0
+    mess = mess.lower()
+    
+    for char in mess:
+        if char in alpha:
+            pos = alpha.index(char)
+            
+            if pos <= 12:
+                pos += 13
+            else:
+                pos = pos % 13
+           
+            newStr += alpha[pos]
+            
+        else:
+            newStr += char    # no rules apply so keep the character
+        
+    return newStr
+
+print(rot13('abcde'))
+print(rot13('nopqr'))
+print(rot13(rot13('Since rot13 is symmetric you should see this message')))

thinkcspy/Chapter-9-Exercises/Python-files/Problem3.py

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+# Runestone.Academy thinkcspy course
+# Chapter 9
+# Problem 3
+
+import string
+
+def count(p):
+    # your code here
+    abc = 0
+    e = 0
+    alphabet = string.ascii_lowercase + string.ascii_uppercase
+    
+    for achar in p:
+        for alphaChar in alphabet:
+            if achar == alphaChar:
+                abc += 1
+        if achar == "e" or achar == "E":
+            e += 1
+            
+    if abc != 0:        
+        ePerAbc = e / abc * 100
+    else:
+        ePerAbc = 0
+    
+    finalMsg = "Your text contains {} alphabetic characters, of which {} ({:.1f}%) are 'e'.".format(abc, e, ePerAbc)
+            
+    return finalMsg
+    
+text = "Bell of the ball"
+print(count(text))

thinkcspy/Chapter-9-Exercises/Python-files/Problem4.py

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+# Runestone.Academy thinkcspy course
+# Chapter 9
+# Problem 4
+
+# your code here
+
+num1 = 1
+product = 0
+
+for n in range(12):
+    num2 = 1
+    row = ""
+
+    for x in range(12):
+        product = num1 * num2
+        row += "{} \t".format(product)
+        num2 += 1
+
+    print(row)
+    num1 += 1

thinkcspy/Chapter-9-Exercises/Python-files/Problem5.py

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+# Runestone.Academy thinkcspy course
+# Chapter 9
+# Problem 
+
+def numDigits(n):
+    # your code here
+    toText = str(n)
+    count = 0
+    
+    for i in range (len(toText)):
+        count += 1
+        
+    return count
+    
+print(numDigits(13))