1. ./file_handle.py
2. ./linear_binary_search.py
3. ./linear_search.py
4. ./search_compare.py
5. ./search_divide.py
6. ./yearborn2.py
7. ./yearborn.py

# Demonstrate file handling exception
# Examples of errors:
#   - file not found
#   - don't have permission on the file
# Sara Sprenkle

import sys

def main():
    
    if len(sys.argv) < 3:
        print("Insufficient arguments")
        print("Usage: python", sys.argv[0],"<infile> <outfile>")
        sys.exit()
    
    #infileName = input("What file do you want to read? ")
    infileName = sys.argv[1]
    
    # put the "correct"/"usual" behavior within the try
    try:
        inFile = open(infileName, "r")
        # typically, we would do some sort of processing of the file here.
        inFile.close()
    except IOError as exc: # exc is the name of the raised exception
        print("Error reading \"" + infileName + "\".")
        # could be a variety of different problems, so print out
        # the exception
        print(exc)
        print(type(exc)) # not helpful output for the user; just for demo purposes
        sys.exit(1)

    #outfileName = input("What file do you want to write? ")
    outfileName = sys.argv[2]
    
    try:
        outFile = open(outfileName, "w")
        # typicall, we would do some sort of processing of the file here.
        outFile.close()
    except IOError as exc:
        print("Error writing \"" + outfileName + "\".")
        print(exc)
        print(type(exc)) # not helpful output for the user; just for demo purposes
        # no need to exit here because there is nothing else to do.
    
main()

# Demonstrate implementations of the linear and binary search
# techniques.
# Sara Sprenkle

# represents that binarySearch did not find the key
NOT_FOUND=-1

def main():
    
    integers = range(1,20,2)
    print("The list to search: ", integers)
    print()
    
    findMeList = [1, 4, 15, 16, 17]
    
    for key in findMeList:
        print("Search for", key)
        print("Linear: Found?", linearSearch(integers, key))
        # binarySearch returns the position the number was found, or -1 if it was
        # not found.  Translate the result from binarySearch to a True or False
        pos = binarySearch(integers, key)
        binFound = pos != NOT_FOUND
        print("Binary: Found?", binFound)
        print()
    

def linearSearch(searchlist, key):
    """
    Returns the position of the key iff it is in the 
    list of integers searchlist.
    """
    for pos in range(len(searchlist)):
        if key == searchlist[pos]:
            return pos
    return NOT_FOUND

def binarySearch(searchlist, key):
    """ Returns the position where key (an int) is found in the list of sorted
    integers searchlist or -1 if key is not in the list. """
    
    low = 0
    high = len(searchlist)-1
    while low <= high:
        mid = (low+high)//2
        valueAtMid = searchlist[mid]
        if valueAtMid == key:
            return mid
        if valueAtMid < key: # search upper half
            low = mid+1
        else: # search lower half
            high = mid-1
    return NOT_FOUND
    
main()

# Demonstrate implementation of the linear search technique.
# Sara Sprenkle

def main():
    
    integers = range(1, 20, 2)
    print("The list we are searching: ", integers)
    print()
    
    findMeList = [1, 4, 15, 16, 17]
    
    for key in findMeList:
        print("Search for", key)
        print("Linear: Found?", linearSearch(integers, key))
        print()


def linearSearch(searchlist, key):
    for elem in searchlist:
        if elem == key:
            return True
    return False

main()

# Compare the linear and binary searching techniques by the number of
# comparisons.
# Not how computer scientists typically analyze algorithms, but want
# to give you some intuition.
# by Sara Sprenkle

def main():

    print("This program helps us to empirically compare search strategies")
    print()

    # The keys I want to search for in a list
    keys = [1, 4, 13, 19, 125, 126, 127, 4999, 9999, 10001, 14999, 19997, 19998, 19999]

    NUM_ENTRIES = 10000
    
    # the list of integers that I'm searching (odd numbers)
    integers = list(range(1,NUM_ENTRIES*2,2))
    print("Creating list of size", NUM_ENTRIES, "starting at 1 and incrementing by 2")
    print()

    print("%6s|%14s" % ("","# Comparisons"))
    print("%6s| %6s %6s" % ("KEY", "LIN", "BIN"))
    print("-"* 24)
    
    total_lin_comp = 0.0
    total_bin_comp = 0.0
    
    for key in keys:
        lin_comp = linearSearch(integers,key)
        bin_comp = binarySearch(integers,key)
        print("{:6d}| {:6d} {:6d}".format(key, lin_comp, bin_comp))
        
        # update the total number of comparisons
        total_lin_comp += lin_comp
        total_bin_comp += bin_comp
    
    print()
    print("ON AVERAGE...")
    print("-"*50)
    print()
    print("The average number of comparisons per search for")
    print("\tlinear search was", total_lin_comp/len(keys))
    print("\tbinary search was", total_bin_comp/len(keys))
    print()
    print("Disclaimer: May not be a completely fair comparison but gives us an idea.")


# Return the number of comparisons required to find the key.
def linearSearch(searchlist, key):
    numChecks = 0
    for elem in searchlist:
        numChecks += 1
        if elem == key:
            return numChecks
    return numChecks

# Return the number of comparisons required to find the key
def binarySearch(searchlist, key):
    low = 0
    high = len(searchlist)-1
    numChecks = 0
    while low <= high:
        mid = (low+high)//2
        numChecks+= 2  # while comparison, next if comparison
        if searchlist[mid] == key:
            return numChecks
        numChecks+=1
        if searchlist[mid] < key:
            low = mid+1
        else:
            high = mid-1
    return numChecks

main()

# Binary search, dividing list in half
# Sara Sprenkle

# represents that binarySearch did not find the key
NOT_FOUND=-1

def main():
    
    integers = range(1,20,2)
    print("The list to search: ", integers)
    print()
    
    findMeList = [1, 4, 15, 16, 17]
    
    for key in findMeList:
        print("Search for", key)
        # binarySearch returns the position the number was found, or -1 if it was
        # not found.  Translate the result from binarySearch to a True or False
        pos = altBinarySearch(integers, key)
        binFound = pos != NOT_FOUND
        print("Binary: Found?", binFound)
        print()

def altBinarySearch(searchlist, key): 
    """Literally divide the list in half. Issues: creates multiple lists.
    Each call to the function requires another list (of half the size of
    the original)."""

    # ran out of elements in the list    
    if len(searchlist) == 0:
        return NOT_FOUND

    low = 0
    high = len(searchlist)-1
    mid = (low+high)/2
    
    valueAtMid = searchlist[mid]
    if valueAtMid == key:
        return mid
    if low == high:
        return NOT_FOUND    

    if searchlist[mid] < key: # search upper half
        return altBinarySearch(searchlist[mid+1:], key)
    else: # search lower half
        return altBinarySearch(searchlist[:mid], key)
        
main()

# Demonstrate validating user input using a few techniques.
# Use if statements when possible.
# Excepts a certain error (ValueError); would not catch other
# exceptions in the except block.
# by CSCI111

import sys

def main():
    print("This program determines your birth year")
    print("given your age and the current year \n")

    try:
        age = int(input("Enter your age: "))
        currentyear = int(input("Enter the current year: "))
    except ValueError:
        print("Error: Your input was not in the correct form.")
        print("Enter integers for your age and the current year")
        sys.exit(1)
    
    if age < 0 or age > 115:
        print("Come on: you have to be a reasonable age.")
    elif currentyear < 0:
        print("You need to have a positive year.")
    else:
        birthyear=currentyear - age
        print("You were either born in", birthyear, "or", birthyear-1)


main()

# Demonstrate validating user input using a few techniques
# Use if statements when possible.
# except statement will "catch" any exception.
# by CSCI111

import sys

def main():
    print("This program determines your birth year")
    print("given your age and the current year \n")

    while True:
        try:
            age = int(input("Enter your age: "))
            currentyear = int(input("Enter the current year: "))
            break
        except:
            print("Error: Your input was not in the correct form.")
            print("Enter integers for your age and the current year")
    
    if age < 0 or age > 115:
        print("Come on: you have to be a reasonable age.")
    elif currentyear < 0:
        print("You need to have a positive year.")
    else:
        birthyear=currentyear - age
        print("You were either born in", birthyear, "or", birthyear-1)


main()