Introduction

In this blog post, we will explore how to solve the LeetCode problem "1375" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

You have a 1-indexed binary string of length n where all the bits are 0 initially. We will flip all the bits of this binary string (i.e., change them from 0 to 1) one by one. You are given a 1-indexed integer array flips where flips[i] indicates that the bit at index i will be flipped in the ith step. A binary string is prefix-aligned if, after the ith step, all the bits in the inclusive range [1, i] are ones and all the other bits are zeros. Return the number of times the binary string is prefix-aligned during the flipping process. Example 1: Input: flips = [3,2,4,1,5] Output: 2 Explanation: The binary string is initially "00000". After applying step 1: The string becomes "00100", which is not prefix-aligned. After applying step 2: The string becomes "01100", which is not prefix-aligned. After applying step 3: The string becomes "01110", which is not prefix-aligned. After applying step 4: The string becomes "11110", which is prefix-aligned. After applying step 5: The string becomes "11111", which is prefix-aligned. We can see that the string was prefix-aligned 2 times, so we return 2. Example 2: Input: flips = [4,1,2,3] Output: 1 Explanation: The binary string is initially "0000". After applying step 1: The string becomes "0001", which is not prefix-aligned. After applying step 2: The string becomes "1001", which is not prefix-aligned. After applying step 3: The string becomes "1101", which is not prefix-aligned. After applying step 4: The string becomes "1111", which is prefix-aligned. We can see that the string was prefix-aligned 1 time, so we return 1. Constraints: n == flips.length 1 <= n <= 5 * 104 flips is a permutation of the integers in the range [1, n].

Explanation

Here's the breakdown of the solution:

• Track the maximum flipped index: Keep track of the maximum index that has been flipped so far.
• Track the number of flipped bits: Keep track of the number of bits that have been flipped to 1.

• Check for prefix alignment: If the maximum flipped index is equal to the number of flipped bits, then the prefix is aligned.

• Runtime Complexity: O(n), where n is the length of the flips array.

• Storage Complexity: O(1)

Code

    def num_times_all_blue(flips: list[int]) -> int:
    """
    Calculates the number of times the binary string is prefix-aligned during the flipping process.
    """
    count = 0
    max_flipped = 0
    flipped_bits = 0

    for i, flip in enumerate(flips):
        max_flipped = max(max_flipped, flip)
        flipped_bits += 1

        if max_flipped == flipped_bits:
            count += 1

    return count