Program to find minimum distance of two given words in a text in Python

Finding the minimum distance between two words in a text is a common string processing problem. The distance is measured as the number of words between any occurrence of the two target words.

Given a text string and two words w1 and w2, we need to find the smallest number of words between any occurrences of these words. If either word is not present, we return -1.

Algorithm

The approach involves tracking the most recent positions of both words as we iterate through the text ?

• Initialize index1 and index2 as None

• Set distance to a large value initially

• For each word in the text:

  • If word matches w1, update index1 and calculate distance with index2 if available

  • If word matches w2, update index2 and calculate distance with index1 if available

• Return the minimum distance found, or -1 if either word is missing

Example

Let's implement the solution to find minimum word distance ?

def solve(text, w1, w2):
    index1 = None
    index2 = None
    distance = float('inf')
    
    for idx, word in enumerate(text.split(" ")):
        if word == w1:
            if index2 is not None:
                distance = min(distance, abs(idx - index2) - 1)
            index1 = idx
        
        if word == w2:
            if index1 is not None:
                distance = min(distance, abs(idx - index1) - 1)
            index2 = idx
    
    if index1 is not None and index2 is not None:
        return distance
    return -1

# Test the function
text = "joy happy power happy joy joy power happy limit"
w1 = "power"
w2 = "limit"
result = solve(text, w1, w2)
print(f"Minimum distance between '{w1}' and '{w2}': {result}")

Minimum distance between 'power' and 'limit': 1

How It Works

In the example text "joy happy power happy joy joy power happy limit":

• power appears at indices 2 and 6

• limit appears at index 8

• Distance between power (index 6) and limit (index 8) = |8 - 6| - 1 = 1

• There is one word "happy" between them

Edge Cases

Let's test when one or both words are missing ?

def solve(text, w1, w2):
    index1 = None
    index2 = None
    distance = float('inf')
    
    for idx, word in enumerate(text.split(" ")):
        if word == w1:
            if index2 is not None:
                distance = min(distance, abs(idx - index2) - 1)
            index1 = idx
        
        if word == w2:
            if index1 is not None:
                distance = min(distance, abs(idx - index1) - 1)
            index2 = idx
    
    if index1 is not None and index2 is not None:
        return distance
    return -1

# Test edge cases
print(solve("hello world python", "hello", "missing"))  # -1 (missing word)
print(solve("cat dog cat dog", "cat", "dog"))           # 0 (adjacent words)
print(solve("one two three four", "one", "four"))       # 2 (two words between)

-1
0
2

Conclusion

This algorithm efficiently finds the minimum distance between two words by tracking their most recent positions during a single pass through the text. The time complexity is O(n) where n is the number of words, making it optimal for this problem.