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$ curl repovive.com/roadmaps/fundamental-algorithms/sliding-window/optimization-jump-left-pointer

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$ curl repovive.com/roadmaps/fundamental-algorithms/sliding-window/optimization-jump-left-pointer

Repovive

Optimization - Jump Left Pointer - Sliding Window | Fundamental Algorithms | Repovive

Repovive.

Fundamental Algorithms8 sections · 294 units2h total

Open in Course

Optimization - Jump Left Pointer

Use hash map to jump left pointer directly.

Jump left directly using a map of last positions.

function lengthOfLongestSubstring(s):
    charIndex = empty map
    left = 0, maxLen = 0

    for right from 0 to s.length - 1:
        if s[right] in charIndex and charIndex[s[right]] >= left:
            left = charIndex[s[right]] + 1
        charIndex[s[right]] = right
        maxLen = max(maxLen, right - left + 1)

    return maxLen

Improvement: Skip multiple characters at once instead of shrinking one by one.

Time: $O(n)$ . Space: $O(\min(n, alphabet))$ .