Zip Solver

Try the zip solver

Rules, restated the way the solver sees them

Zip asks for a single path that starts on cell 1, passes through every cell exactly once, and visits the numbered cells in increasing order. Walls are segments on cell borders that the path may not cross. Every step in the 37 archived solutions is orthogonal, and the tool only moves up, down, left or right. This is a Hamiltonian path problem on a grid graph with some edges removed, which sounds grand but is small enough at these sizes to search directly: an 8×8 board has 64 cells, and the numbers rule out any route that touches a number out of turn.

The search is a plain depth-first search. It starts on 1 and extends the path one cell at a time, trying the four neighbours in a fixed order, refusing any cell already used, any border with a wall, and any numbered cell that is not the next number due. When it gets stuck it backs up one cell and tries the next option. It stops at the first path that covers every cell after visiting all the numbers. It does not go on to look for a second path; on real boards that does not matter, because when we ran an exhaustive search on all 37 archived boards each had exactly one.

Entering numbers and walls

The board is entered in two passes, and both matter.

• Size first. Count the columns on the real board; 6, 7 and 8 all occur and the tool cannot infer the size from the numbers.
• Numbers in order. Tap the cell where 1 sits, then 2, then 3. The tool places the next number on each tap; tapping a numbered cell again removes it and renumbers the rest, which is the quickest way to fix a slip.
• Walls last. Switch to the wall tool and tap the border between two cells. A wall is drawn on the shared edge. Walls on the outer boundary of the board are meaningless and cannot be placed.
• Check the count. Under the board the tool shows how many numbers and walls you have entered; compare both with the real board. A missing wall makes the board looser than the real one, so it can produce a wrong path rather than an error — the wall count is the one to check.

Why walls matter more than numbers

Newcomers concentrate on the numbers, but on boards with walls — 26 of the 37 in our archive — the walls often do the real work. A wall on a cell's border removes one of its exits, and a cell with only one exit is a dead end that the path can only enter as its last cell or leave as its first — so any such cell that is not the highest number must be cell 1, and if it is neither, the board is impossible. Walls in a line can seal off a whole band of the board, leaving it one or two openings, which fixes where the path enters and leaves that region.

The solver, of course, does not need to notice any of this; it simply finds that the alternatives fail. But when you compare its path with your own failed attempts, the walls are almost always where they diverge. If your attempts kept leaving a single unreachable cell in a corner, that corner had a wall you were reading as a border, or a border you were reading as a wall.

Reading the drawn path

The result shows the whole route with the numbered cells marked, so you can see which cells each segment claimed. Trace it from 1 and notice where the path makes what looks like a detour: a loop out to an edge and back before continuing toward the next number. Those detours are never optional. They exist because the cells on the detour would otherwise be unreachable later, and the moment a detour is forced is exactly the moment the parity rule or the corner rule applies. Learning to see the detour before you draw the segment is what saves the most redrawing.

The tool reports the first path it finds and does not check for others; since every archived board has had a single solution, that path is the answer. If it says no path covers every cell, a wall or number is misplaced, the numbers were tapped in the wrong order, or the size is wrong.

A note on speed

The temptation in Zip is to draw first and erase later; the rules reward the opposite.

Edge cells have three neighbours; if one is walled off, the edge cell behaves like a corner. Walk the perimeter of the board and mark every forced segment.— From the Zip guide on HintSheet

Related tools

Zip shares its forced-move logic with two other LinkedIn games and the site has a solver for each. Queens is a placement puzzle rather than a path puzzle but uses the same style of elimination, and Tango applies it to a two-symbol grid. Every game's daily solution is on its answer page, and the Zip archive keeps every board since 3 September 2026 with the path drawn — a better practice set than a random-board generator, because each of those boards has exactly one solution.

A real board, segment by segment: Zip #535

Zip #535, 3 September 2026, was a 7×7 with nine numbers laid out in a deliberate pattern: 1, 2 and 3 across the second row at columns four, six and two; 4, 5 and 6 across the fourth row at columns six, four and two; 7, 8 and 9 across the sixth row at columns two, six and four. Its twelve walls are mostly two straight lines of five: one under row two and one under row five, each spanning columns two to six, plus single walls under row three at column two and under row four at column six. It looks like a grid of nine dots and it plays like a maze.

The two wall lines are the whole puzzle. The top two rows are sealed from the rest of the board except through columns one and seven, and so are the bottom two rows. 1, 2 and 3 all sit in the top band, so the path must collect all fourteen top-band cells before it leaves. The obvious hop from 1 to 2 — two cells to the right — is correct. From 2 the path goes out to column seven, up into the top-right corner and left along the top row to column three, then drops into 3. 3→4 collects the top-left corner and leaves the band down column one. The bottom band holds 7, 8 and 9, and since 9 is the last number the path enters that band once, down column one, and never leaves: 7→8 runs along the bottom row and up into 8, and 8→9 is two steps left.

Enter #535 into the tool from the archive and watch the drawn path: once you see that the wall lines turn the top and bottom of the board into bands with two openings each, everything after that is bookkeeping. Boards that feel hard are often boards where a band or corner has to be claimed early by a segment that does not seem to need it.

Checkerboard parity, explained once

Colour the cells of any Zip board like a chessboard. Every step of the path moves from a light cell to a dark cell or back, so a path through all the cells alternates colours the entire way. On a 7×7 board there are 25 cells of one colour and 24 of the other; a path covering all 49 must start and end on the majority colour, and so cell 1 and the highest number must both sit on it. On an even board — 6×6 or 8×8 — the two colours are equal and the endpoints must be different colours. Any solvable board respects this, so it is not a test of the board, but the rule earns its keep in the middle of a solve: the number of steps between one number and the next is even if the two sit on the same colour and odd if they sit on different colours, so a route of the wrong length is impossible, however legal each individual step looks.

The solver does not reason about parity — it simply finds that the wrong routes fail — but it is the one piece of Zip reasoning worth doing consciously, because it rules out entire routes before you draw a single cell of them. On #535, 6 (row four, column two) and 7 (row six, column two) are on the same colour, so 6→7 must take an even number of steps. The direct two-step route down column two is blocked by the wall under row five, so the path goes left to column one, down to the bottom row and back up into 7: six steps, even, as required.

What the tool logs, and what it does not

For the curious: under the board the tool shows a running count of the numbers and walls you have entered, which is the quickest way to check your entry against the real board. It does not report how long the search took or how many routes it tried. The board you enter is solved in your browser and is not sent anywhere; the share buttons that appear after a solve share only the page link and a line naming the board size.

Frequently asked questions