1. search2.py
2. search_divide.py
3. search.py

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

# represents that the search 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)
        pos = linearSearch(integers, key))
        linFound = pos != NOT_FOUND
        print("Linear: Found?", linFound)
        # binarySearch returns the position the number was found, or -1 if it was
        # not found.  
        pos = binarySearch(integers, key)
        #Translate the result from binarySearch to a True or False
        binFound = pos != NOT_FOUND
        print("Binary: Found?", binFound)
        print()
    

def linearSearch(searchlist, key):
    """Returns the position where key (an int) is found in the list of
    integers or -1 if key is not in the list."""
    for index in range(len(searchlist)):
        if searchlist[index] == key:
            return index
    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()

# 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 implementation of the linear search technique.
# Two implementations: one returns either True or False; 
# the other returns the position where the element was found
# Sara Sprenkle

NOT_FOUND = -1

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)
        found = linearSearch(integers, key)
        print("Linear: Found?", found)
        if found:
            print("Pos: ", linearSearchReturnPos(integers, key))
        # You probably wouldn't really use both implementations
        # of linear search.  Just for demonstration
        print()


def linearSearch(searchlist, key):
    """Returns True iff the key is in searchlist."""
    for elem in searchlist:
        if elem == key:
            return True
    return False

def linearSearchReturnPos(searchlist, key):
    """Returns the position of the key in searchlist, if found;
    -1 if not found."""
    for pos in range(len(searchlist)):
        if searchlist[pos] == key:
            return pos
    return NOT_FOUND
    
main()