def linear_search(L,x):
    # Scan the list L from left to right and compare it with x. 
    # If we find x, return the index. If not, return -1.
    for i in range(len(L)): # i = 0, 1, ..., len(L)-1
        if x==L[i]:
            return i
    
    # Will only arrive here, if x is not in L    
    return -1

def linear_search_returnAll(L,x):
    # Scan the list L from left to right and compare it with x. 
    # If we find x, store index in result list. If not, return empty list.
    result=[]
    for i in range(len(L)): # i = 0, 1, ..., len(L)-1
        if x==L[i]:
            result.append(i)
    
    # Will only arrive here, if x is not in L    
    return result

def binary_search(L,x):
    ''' Input: List L, sorted in ascending order; and element x
        Output: index of x in L, or -1 otherwise
        1. Test whether x is less than the median (if it is equal, we are done).
        2. Continue to search the half of the list that x is in.
        3. We are done when the correct side of the list is empty.
    '''
    left = 0  # left index of "zoomed-in" portion
    right = len(L)-1 # right index of "zoomed-in" portion
    #print "outside: left=", left, ", right=",right
    
    while left<=right: ## not finished
        median = (left+right)/2 # index of median; automatically rounded down
        #print "left=", left, ", right=",right
        if x<L[median]: 
            # throw away right portion, continue in left portion
            right = median-1
        elif x==L[median]:
            # Found it! Return index
            return median    
        else: # x>L[median]     
            # throw away left portion, continue in right portion
            left = median+1
    # x not found
    return -1       


def binary_search_rec(L, x, left, right):
    if left>right: # empty portion of L
        return -1
    
    median = (left+right)/2
    if x<L[median]:
        # search left
        return binary_search_rec(L,x,left, median-1)
    elif x==L[median]:
        #Found it!
        return median
    else:
        # search right
        return binary_search_rec(L,x,median+1,right)



'''


my_list=[7, -3, 5, 42, 11,33, 11110, 5, 7, 8]


print linear_search(my_list,5)
print linear_search(my_list,7)
print linear_search(my_list,8)
print linear_search(my_list,9) # not in list

print linear_search_returnAll(my_list,5)
print linear_search_returnAll(my_list,7)
print linear_search_returnAll(my_list,8)
print linear_search_returnAll(my_list,9) # not in list

############# Now testing binary search
print "Now testing binary search"
sorted_list = [-3, 5, 8, 20, 21, 42,51,60, 61]
print "sorted=", binary_search(sorted_list,8)
'''
 
sorted_list = [-3, 5, 8, 20, 21, 42,51,60, 61]

print "sorted=", binary_search_rec(sorted_list,8, 0,len(sorted_list)-1)