Create Integer Zigzag

An array a[0], a[1], a[2], … is a zigzag (or “wiggle sort”) if a[0] ≤ a[1] ≥ a[2] ≤ a[3] ≥ a[4] ≤ …. Odd-indexed elements are peaks (≥ both neighbors); even-indexed elements are valleys (≤ both neighbors). The validity check verifies this exact condition.

Sort the array ascending. Then swap pairs at positions (1,2), (3,4), (5,6), …. Example: [1,5,3,8,2,7] sorted = [1,2,3,5,7,8], swap (1,2)→(2,1) → [1,3,2,5,7,8], swap (3,4)→(5,7)→(7,5) → [1,3,2,7,5,8]. Wait – that’s wrong. The actual swap is index (i, i+1) for odd i. So [1,2,3,5,7,8] swap (1,2): [1,3,2,5,7,8], swap (3,4): [1,3,2,7,5,8]. That’s a valid zigzag (1≤3≥2≤7≥5≤8). Sort is O(n log n).

Walk left-to-right. At each position i, check the invariant: even-i needs a[i] ≤ a[i+1]; odd-i needs a[i] ≥ a[i+1]. If violated, swap a[i] and a[i+1]. O(n) time. The greedy variant can leave duplicates in problematic positions where strict zigzag is impossible – the validity check will flag this.

If your input has many duplicates of the same value, no rearrangement can satisfy strict ≤/≥ at every position. Example: [5, 5, 5, 5] can only be [5, 5, 5, 5] regardless of algorithm – and that’s not a strict zigzag. The tool emits an info toast and the stats line marks the failure index.

Strict (this tool): < and > required. Non-strict: ≤ and ≥. We use the non-strict version (≤, ≥) in the validity check because strict is impossible whenever any adjacent values are equal – which would mark even valid-looking outputs invalid. The validity check follows the standard “wiggle sort” definition used in LeetCode 280.

Builds an ascending sequence from start to end (in step increments), then descends back to start, then ascends, alternating. “Bounces” controls how many round-trip segments to append after the first ascent. Bounces = 0 → just [1, 2, …, 10]. Bounces = 1 → [1, …, 10, 9, …, 1]. Bounces = 2 → [1, …, 10, 9, …, 1, 2, …, 10].

Yes. The zigzag pattern compares relative values, so signs don’t matter. [-5, 3, -2, 8] works the same as [1, 2, 3, 4] would, conceptually.

Newlines, commas, spaces, semicolons, or any combination. Non-integer tokens are silently dropped; the live counter shows the drop count.

No. All processing happens locally in your browser – nothing is sent to a server, logged, or stored, and the tool keeps working offline once the page has loaded.