🚀 DSA Progress Update | Solved 3 LeetCode Problems

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🚀 DSA Progress Update | Solved 3 LeetCode Problems

Today's LeetCode session was focused on strengthening my understanding of three fundamental problem-solving patterns that frequently appear in technical interviews.

✅ Problems Solved

🔹 682. Baseball Game

Pattern: Stack
Built a score history using a stack to efficiently process operations such as +, D, and C.
Time Complexity: O(n)

stack = []

for op in operations:
    if op == "+":
        stack.append(stack[-1] + stack[-2])
    elif op == "D":
        stack.append(2 * stack[-1])
    elif op == "C":
        stack.pop()
    else:
        stack.append(int(op))

return sum(stack)

🔹 1456. Maximum Number of Vowels in a Substring of Given Length

Pattern: Sliding Window
Optimized the brute-force approach by maintaining a fixed-size window and updating the vowel count in constant time.
Time Complexity: O(n)

vowels = {'a', 'e', 'i', 'o', 'u'}

count = sum(1 for ch in s[:k] if ch in vowels)
maximum = count

for i in range(k, len(s)):
    if s[i-k] in vowels:
        count -= 1
    if s[i] in vowels:
        count += 1
    maximum = max(maximum, count)

return maximum

🔹 134. Gas Station

Pattern: Greedy Algorithm
Learned how tracking the fuel balance helps identify the only valid starting station while solving the problem in linear time.
Time Complexity: O(n)

if sum(gas) < sum(cost):
    return -1

start = 0
tank = 0

for i in range(len(gas)):
    tank += gas[i] - cost[i]

    if tank < 0:
        start = i + 1
        tank = 0

return start

💡 Key Takeaways

✔️ Choosing the right algorithmic pattern is often more important than writing more code.

✔️ Today's practice reinforced three essential interview concepts:

Stack
Sliding Window
Greedy Algorithm

Every problem I solve improves not only my coding skills but also my ability to analyze problems, optimize solutions, and think like a software engineer.

I'm committed to solving LeetCode problems consistently and documenting my progress as I continue growing in Data Structures & Algorithms.