Print Substrings that are Prefix of the Given String - Python Last Updated : 31 Jan, 2025 Summarize Comments Improve Suggest changes Share Like Article Like Report The task of printing the substrings that are prefixes of a given string involves generating all the possible substrings that start from the first character of the string and end at any subsequent position.For example, if the given string is s = "hello", the prefixes of the string would include "h", "he", "hel", "hell", and "hello". We want to print these prefixes in order, starting from the smallest to the largest with the entire string being the final prefix.Using SlicingSlicing allows us to extract any part of the string from the start to any given position. This enables us to progressively generate prefixes by increasing the substring length from the start to the full string. Python s = "abdabc" for i in range(1, len(s) + 1): print(s[:i]) Outputa ab abd abda abdab abdabc Table of ContentUsing sliding window Using string comparisonUsing hash set Using sliding window Sliding window extract substrings of different sizes and checks if each substring matches the prefix of the string. It expands the window step by step, performing comparisons for each window size. This method involves slicing and checking substrings at each step. Python s = "ababc" n = 1 # Window size # Loop through all window sizes while n <= len(s): # Check for prefix matches for i in range(len(s) - n + 1): if s[i:i+n] == s[:n]: print(s[i:i+n]) n += 1 # Increase window size Outputa a ab ab aba abab ababc Explanation:while n <= len(s) start a loop that iterates over all possible window sizes from 1 to the length of s .for i in range(len(s) - n + 1) for each window size, slide through the string s to check substrings.if s[i:i+n] == s[:n] compare the current substring to the prefix (first n characters) of the s .print(s[i:i+n]) if a match is found then print the substring.Using string comparisonString comparison finds prefix substrings by slicing the string at each position. It iterates through the string comparing each substring with its corresponding prefix. This approach is simple way to extract and print all prefixes of a string. Python s = "ababc" for i in range(len(s)): if s[:i+1] != s[:i]: print(s[:i+1]) Outputa ab aba abab ababc Explanation:for i in range(len(s)) loop goes through each character in s, starting from the first index.if s[:i+1] != s[:i] checks if the current prefix (s[:i+1]) is different from the previous one (s[:i]) and ensures that duplicates are avoided by only printing when a new prefix appears.print(s[:i+1]) prints the current prefix substring.Using hash set This method uses a hash set to store unique prefixes of a string. As it loops through the string it checks each prefix and prints it only if it hasn’t been seen before. The use of the set ensures that duplicates are avoided efficiently. Python s = "ababc" p = set() # Iterate through the `s` for i in range(1, len(s) + 1): if s[:i] not in p: print(s[:i]) p.add(s[:i]) Outputa ab aba abab ababc Explanation:if s[:i] not in p checks if the current prefix s[:i] is not already in the set p.print(s[:i]) prints the unique prefix.p.add(s[:i]) adds the current prefix to the set p to ensure no duplicates are printed. Comment More infoAdvertise with us Next Article Print Substrings that are Prefix of the Given String - Python R rituraj_jain Follow Improve Article Tags : Technical Scripter Python Python Programs Technical Scripter 2018 prefix python-string substring +3 More Practice Tags : python Similar Reads Python Tutorial - Learn Python Programming Language Python is one of the most popular programming languages. Itâs simple to use, packed with features and supported by a wide range of libraries and frameworks. Its clean syntax makes it beginner-friendly. 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