General Guide

Definition

A natural extension of Two Pointer patterns with a tighter focus, where you manage an array of values (i.e. your window).

When problem asks about contiguous segments (substring, subarray, group of consecutive elements) its pretty much asking you to solve a sliding window problem.

Key attributes

• Never revisit the same element twice.
  • this is what makes this algorithm an O(N) time complexity solution

Fixed Window Template

function slidingWindow(input, windowSize) {

    answer = window = input.reduce((a, b) => a + b, 0);

    for(right of range(windowSize, input.length)) {
        left = right - windowSize
        remove left from window
        add right to window
        answer = max(answer, window)
    }

    return ans;
}

Dynamic Sliding Window Template

function slidingWindowFlexible(input) {

    initialize window and answer;

    let left = 0;

    for right in range(input.length) {
        add right to window
        while invalid(window):
            remove left from window;
            left += 1
        answer = max(answer, window)
    }

    return answer;

}