require "table2"
local fmt = require "fmt"

local function zigzag(n)
    local r = table.rep(n * n, 0)
    local i = 0
    local n2 = n * 2
    for d = 1, n2 do
        local x = d - n
        if x < 0 then x = 0 end
        local y = d - 1
        if y > n - 1 then y = n - 1 end
        local j = n2 - d
        if j > d then j = d end
        for k = 0, j - 1 do
            if d & 1 == 0 then
                r[(x + k) * n + y - k + 1] = i
            else
                r[(y - k) * n + x + k + 1] = i
            end
            i += 1
        end
    end
    return r
end

local n = 5
local w = #tostring(n * n - 1)
local i = 0
for zigzag(n) as e do
    fmt.write($"%{w}d ", e)
    if i % n == n - 1 then print() end
    i += 1
end