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K Consecutive Bit Flips

Certification: Advanced Level Accuracy: 0% Submissions: 0 Points: 15

Write a C program to find the minimum number of K consecutive bit flips needed to make all bits in a binary array equal to 1. A K-bit flip consists of choosing a subarray of length K and flipping every bit in it (0 becomes 1, 1 becomes 0). If it's impossible to make all bits 1, return -1.

Example 1
    
      
  • Input: nums = [0,1,0], K = 1
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  • Output: 2
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  • Explanation: 
    • Initial array: [0,1,0]. 
    • Flip bit at index 0: [1,1,0]. 
    • Flip bit at index 2: [1,1,1]. 
    • Total flips needed: 2.
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Example 2
    
      
  • Input: nums = [1,1,0], K = 2
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  • Output: -1
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  • Explanation: 
    • Initial array: [1,1,0]. 
    • We can flip indices 0-1: [0,0,0] or indices 1-2: [1,0,1]. 
    • No matter what we do, we cannot make all bits 1. 
    • Therefore, return -1.
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Constraints
    
      
  • 1 ≤ nums.length ≤ 30000
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  • 1 ≤ K ≤ nums.length
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  • nums[i] is 0 or 1
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  • Time Complexity: O(n)
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  • Space Complexity: O(n)
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ArraysPwCPhillips
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Hint
Solution
Solution Hints
    
      
  • Use a greedy approach: scan from left to right
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  • When you encounter a 0, you must flip the K-length subarray starting from that position
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  • Keep track of how many flips affect each position using a difference array
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  • Use the flip count to determine the current state of each bit
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  • If you can't perform a flip (not enough elements left), return -1
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  • Count the total number of flips performed
    •

Steps to solve by this approach:

 Step 1: Initialize variables to track total flips and current flip count affecting each position
 Step 2: Use a difference array to efficiently track when flip effects start and end
 Step 3: Iterate through the array from left to right, updating flip count at each position
 Step 4: Calculate the current effective bit value after considering all active flips
 Step 5: If current bit is 0, perform a K-flip starting from current position (if possible)
 Step 6: Update the difference array to mark when the flip effect ends
 Step 7: Return total flips if successful, or -1 if impossible to make all bits 1

Submitted Code :