# (Uses str.find.)
def get_indices(text, pattern):
    '''Return a list containing the indices where str pattern appears in str
    text.  Overlapping instances of pattern should be counted.  For example,
    get_indices("abcabcabc", "bc") --> [1, 4, 7]
    get_indices("bbbbbbb", "bb") --> [0, 1, 2, 3, 4, 5]'''

    # Accumulate the indices of occurrences here.
    indices = []
    # The position of the next occurrence of pattern within text.
    index = text.find(pattern, 0)
    
    # Keep looking until there are no more occurrences.
    while index != -1:
        # Record this occurrence.
        indices.append(index)
        # Advance past this occurrence and look for the next one.
        index = text.find(pattern, index + 1)
        
    return indices

# (Does not use str.find.)
def basic_stringmatch(text, pattern):
    '''Find all instances of the string pattern in the string 
    text.  Return a list containing the starting indices of all
    matches.  
    
    This version iterates through text one character at a time, 
    checking if the pattern matches starting at that character.
    It checks the entire pattern at each character.'''
    
    matches = []
    
    # Iterate through text
    for index in range(len(text) - len(pattern) + 1):
        
        # Check if the pattern matches starting at this character
        match = True
        for p_index in range(len(pattern)):
            if text[index + p_index] != pattern[p_index]:
                match = False            
        if match:
            matches.append(index)

    return matches


def early_exit_stringmatch(text, pattern):
    '''Find all instances of the string pattern in the string 
    text.  Return a list containing the starting indices of all
    matches.  
    
    This version iterates through text one character at a time, 
    checking if the pattern matches starting at that character.
    It stops checking the pattern when a mismatch is detected.'''
    
    matches = []
    
    # Iterate through text
    for index in range(len(text) - len(pattern) + 1):
        
        # Check if the pattern matches starting at this character
        p_index = 0
        while p_index < len(pattern) and \
              text[index + p_index] == pattern[p_index]:
            p_index = p_index + 1
            
        # The pattern matches if the previous loop iterated through
        # the entire pattern.
        if p_index == len(pattern):
            matches.append(index)

    return matches

def main():

    print(get_indices("abcabcabc", "bc"), "sb", [1,4,7])
    print(get_indices("bbbbbbb", "bb"), "sb", [0,1,2,3,4,5])
    print(get_indices("bbbbbbb", "aa"), "sb", [])
    print(get_indices("abc", "abcde"), "sb", [])
    print(get_indices("", ""), "sb", [0])
    print(get_indices("abcabcabc", "ab"), "sb", [0,3,6])

    print(basic_stringmatch("CTACAATATATCGTATCATATCC","ATATC"), "sb",[7,17])
    print(basic_stringmatch("ATATAT","AT"), "sb", [0,2,4])

    print(early_exit_stringmatch("CTACAATATATCGTATCATATCC","ATATC"), "sb",[7,17])
    print(early_exit_stringmatch("ATATAT","AT"), "sb", [0,2,4])

main()