Program to count items matching a rule using Python

Suppose we have an array nums, where each nums[i] contains three elements [type_i, color_i, name_i]. These are describing the type, color, and name of the ith item. We also have a rule represented by two other strings, ruleKey and ruleValue. Now we can say the ith item matches the rule if one of the following is true ?

• ruleKey = "type" and ruleValue = type_i.

• ruleKey = "color" and ruleValue = color_i.

• ruleKey = "name" and ruleValue = name_i.

We have to find the number of items that match the given rule.

So, if the input is like ?

And ruleKey = "color", ruleValue = "blue", then the output will be 2 as there are two matches: ["Bike","blue","ElecB"] and ["Bike","blue","TVS"].

Method 1: Using Index-Based Approach

We can solve this by mapping the ruleKey to its corresponding index and then checking each item ?

def solve(items, ruleKey, ruleValue):
    count = 0
    rule_index = {"type": 0, "color": 1, "name": 2}
    
    index = rule_index[ruleKey]
    for item in items:
        if item[index] == ruleValue:
            count += 1
    
    return count

items = [["Bike","blue","ElecB"],["Car","silver","Sumo"],["Bike","blue","TVS"]]
ruleKey = "color"
ruleValue = "blue"
print(solve(items, ruleKey, ruleValue))

2

Method 2: Using List Comprehension

We can use list comprehension for a more concise solution ?

def solve(items, ruleKey, ruleValue):
    rule_index = {"type": 0, "color": 1, "name": 2}
    index = rule_index[ruleKey]
    
    return sum(1 for item in items if item[index] == ruleValue)

items = [["Bike","blue","ElecB"],["Car","silver","Sumo"],["Bike","blue","TVS"]]
ruleKey = "type"
ruleValue = "Bike"
print(solve(items, ruleKey, ruleValue))

2

Method 3: Using Filter Function

We can also use Python's built-in filter function ?

def solve(items, ruleKey, ruleValue):
    rule_index = {"type": 0, "color": 1, "name": 2}
    index = rule_index[ruleKey]
    
    matching_items = filter(lambda item: item[index] == ruleValue, items)
    return len(list(matching_items))

items = [["Bike","blue","ElecB"],["Car","silver","Sumo"],["Bike","blue","TVS"]]
ruleKey = "name"
ruleValue = "ElecB"
print(solve(items, ruleKey, ruleValue))

1

Comparison

Conclusion

Use the index-based approach for clarity and efficiency. The list comprehension method offers concise code, while the filter function provides a functional programming approach. All methods have O(n) time complexity where n is the number of items.