Common Problem Solving Patterns (Sliding Window, Two Pointers, etc.)

Common Problem Solving Patterns (Sliding Window, Two Pointers, etc.)

• Sliding Window: maintain a window with O(1) updates to solve subarray/substring problems
• Two Pointers: converge/diverge for pairs/dups in sorted data
• Fast & Slow Pointers: cycle detection (Floyd), middle of list
• Binary Search on Answer: search a monotonic answer space

// Sliding window: longest substring with <= K distinct chars
function longestKDistinct(s, K){
  const freq=new Map(); let best=0, l=0
  for(let r=0;r<s.length;r++){
    freq.set(s[r],(freq.get(s[r])||0)+1)
    while(freq.size>K){
      const c=s[l++]; const v=freq.get(c)-1; v?freq.set(c,v):freq.delete(c)
    }
    best=Math.max(best, r-l+1)
  }
  return best
}

Recognizing patterns reduces time-to-solution dramatically and guides complexity expectations.