Lua 5.3、57522
问题刚发布时,我实际上就开始对此进行研究,但是直到Brain-Flak周年纪念日才忘记了。
-- 64 gives all results through 10000 (should run in about 1 second)
-- 78 gives all results through 100000 (should run in about 20 seconds)
-- 90 gives all results through 1000000 (should run in about 200 seconds)
-- Note: Timings may not be accurate, as the are not updated every time new cases are added.
local k_max_len = 64
local k_limit = 10000
local pre = os.clock()
local function compute_multiplier_helper(prefix, suffix, m)
  if m == 2 then
    prefix[#prefix + 1] = "("
    suffix[#suffix + 1] = "){}"
  elseif m % 2 == 0 then
    prefix[#prefix + 1] = "("
    compute_multiplier_helper(prefix, suffix, m // 2)
    suffix[#suffix + 1] = "){}"
  else
    suffix[#suffix + 1] = ")"
    compute_multiplier_helper(prefix, suffix, m - 1)
    prefix[#prefix + 1] = "("
    suffix[#suffix + 1] = "{}"
  end
end
local function compute_multiplier(m)
  local prefix = {}
  local suffix = {}
  compute_multiplier_helper(prefix, suffix, m)
  return table.concat(prefix), table.concat(suffix)
end
local multipliers = {}
for m = 2, k_limit do
  -- Including all factors, not just primes.
  -- This did improve a few numbers, although none in the ppcg test set.
  local prefix, suffix = compute_multiplier(m)
  local mult = {prefix = prefix, suffix = suffix, m = m, cost = #prefix + #suffix}
  table.insert(multipliers, mult)
end
table.sort(multipliers, function(a, b) return a.cost < b.cost end)
local poly_multipliers = {}
poly_multipliers[1] = {m = 1, s = "({})", l = 4}
for m = 2, k_limit do
  local prefix, suffix = compute_multiplier(m)
  local s = prefix .. "({})" .. suffix
  assert(#s <= 4 * m)
  poly_multipliers[m] = {m = m, s = s, l = #s}
end
poly_multipliers[k_limit + 1] = {m = 0, s = "", l = 0}
table.sort(poly_multipliers, function(a, b) return a.l < b.l end)
local pcache = {}
local plen_cache = {}
local function register_push(prefix, suffix, value, pvalue)
  if value > 1500000 or value < -1500000 then return end
  local old_res = pcache[value]
  if old_res == nil then
    local res = {prefix = prefix, suffix = suffix, value = value, pvalue = pvalue}
    pcache[value] = res
    local length = #prefix + #suffix
    local lcache = plen_cache[length]
    if lcache == nil then
      lcache = {}
      plen_cache[length] = lcache
    end
    lcache[#lcache + 1] = res
  end
end
local function get_pushes(length)
  return ipairs(plen_cache[length] or {})
end
register_push("", "()", 1, 0)
register_push("", "<()>", 0, 0)
local function triangle(n)
  return (n * (n + 1)) // 2
end
local function process(length)
  -- basic
  for _, res in get_pushes(length - 2) do
    register_push(res.prefix, res.suffix .. "()", res.value + 1, res.pvalue)
    register_push(res.prefix, "[" .. res.suffix .. "]", -res.value, res.pvalue)
  end
  -- multiplication by constant (precomputed)
  for _, mult in ipairs(multipliers) do
    local cost = mult.cost
    if length - cost >= 4 then
      local m, prefix, suffix = mult.m, mult.prefix, mult.suffix
      for _, pus in get_pushes(length - cost) do
        local name = prefix .. pus.suffix .. suffix
        register_push(pus.prefix, name, pus.value * m, pus.pvalue)
      end
    else
      break
    end
  end
  -- residue 2 mod3 trick (Neil)
  -- ((n)()){}{}
  --  (n)        -- push n
  -- (   ())     -- push n + 1
  --        {}{} -- (n + 1) + (n + 1) + n
  if length - 10 >= 2 then
    for _, res in get_pushes(length - 10) do
      local name = "((" .. res.suffix .. ")()){}{}"
      register_push(res.prefix, name, 3 * res.value + 2, res.pvalue)
    end
  end
  -- residue 1 mod3 trick (Wheat Wizard)
  -- ((n)()()){}{}
  --  (n)          -- push n
  -- (   ()())     -- push n + 2
  --          {}{} -- (n + 2) + (n + 2) + n
  -- not useful, but fast...
  if length - 12 >= 2 then
    for _, res in get_pushes(length - 12) do
      local name = "((" .. res.suffix .. ")()()){}{}"
      register_push(res.prefix, name, 3 * res.value + 4, res.pvalue)
    end
  end
  -- residue 2 mod5 trick (tehtmi)
  -- (((n)){}()){}{}
  --   (n)           -- push n
  --  (   )          -- push n
  -- (     {}())     -- push 2n + 1
  --            {}{} -- (2n + 1) + (2n + 1) + n
  -- [[
  if length - 14 >= 2 then
    for _, res in get_pushes(length - 14) do
      local name = "(((" .. res.suffix .. ")){}()){}{}"
      register_push(res.prefix, name, 5 * res.value + 2, res.pvalue)
    end
  end
  -- ]]
  -- residue 4 mod5 trick (tehtmi)
  -- (((n)()){}){}{}
  --   (n)           -- push n
  --  (   ())        -- push n + 1
  -- (       {})     -- push 2n + 2
  --            {}{} -- (2n + 2) + (2n + 2) + n
  -- [[
  if length - 14 >= 2 then
    for _, res in get_pushes(length - 14) do
      local name = "(((" .. res.suffix .. ")()){}){}{}"
      register_push(res.prefix, name, 5 * res.value + 4, res.pvalue)
    end
  end
  -- ]]
  -- residue 6 mod7 trick (tehtmi)
  -- ((((n)())){}{}){}{}
  --    (n)              -- push n
  --   (   ())           -- push n + 1
  --  (       )          -- push n + 1
  -- (         {}{})     -- push 3n + 3
  --                {}{} -- (3n + 3) + (3n + 3) + n
  -- [[
  if length - 18 >= 2 then
    for _, res in get_pushes(length - 18) do
      local name = "((((" .. res.suffix .. ")())){}{}){}{}"
      register_push(res.prefix, name, 7 * res.value + 6, res.pvalue)
    end
  end
  --]]
  -- residue 4 mod7 trick (tehtmi)
  -- ((((n))()){}{}){}{}
  --    (n)              -- push n
  --   (   )             -- push n
  --  (     ())          -- push n + 1
  -- (         {}{})     -- push 3n + 2
  --                {}{} -- (3n + 2) + (3n + 2) + n
  -- [[
  if length - 18 >= 2 then
    for _, res in get_pushes(length - 18) do
      local name = "((((" .. res.suffix .. "))()){}{}){}{}"
      register_push(res.prefix, name, 7 * res.value + 4, res.pvalue)
    end
  end
  --]]
  -- residue 2 mod7 trick (tehtmi)
  -- ((((n))){}{}()){}{}
  --    (n)              -- push n
  --   (   )             -- push n
  --  (     )            -- push n
  -- (       {}{}())     -- push 3n + 1
  --                {}{} -- (3n + 1) + (3n + 1) + n
  -- [[
  if length - 18 >= 2 then
    for _, res in get_pushes(length - 18) do
      local name = "((((" .. res.suffix .. "))){}{}()){}{}"
      register_push(res.prefix, name, 7 * res.value + 2, res.pvalue)
    end
  end
  --]]
  -- triangle numbers (?)
  --(n){({}[()])}{}
  --(n)              -- push n
  --   {        }    -- sum and repeat
  --    (      )     -- push
  --     {}[()]      -- top - 1
  --             {}  -- pop 0
  if length - 14 >= 2 then
    for _, res in get_pushes(length - 14) do
      if res.value > 0 then
        local code = "{({}[()])}{}"
        register_push(res.prefix .. "(" .. res.suffix .. ")", code, triangle(res.value - 1), res.pvalue + res.value)
        register_push(res.prefix, "(" .. res.suffix .. ")" .. code, triangle(res.value), res.pvalue)
        register_push("", res.prefix .. "(" .. res.suffix .. ")" .. code, triangle(res.value) + res.pvalue, 0)
      end
    end
  end
  -- negative triangle numbers (tehtmi)
  --(n){({}())}{}
  --(n)            -- push n
  --   {      }    -- sum and repeat
  --    (    )     -- push
  --     {}()      -- top + 1
  --           {}  -- pop 0
  if length - 12 >= 2 then
    for _, res in get_pushes(length - 12) do
      if res.value < 0 then
        local code = "{({}())}{}"
        register_push(res.prefix .. "(" .. res.suffix .. ")", code, -triangle(-res.value - 1), res.pvalue + res.value)
        register_push(res.prefix, "(" .. res.suffix .. ")" .. code, -triangle(-res.value), res.pvalue)
        register_push("", res.prefix .. "(" .. res.suffix .. ")" .. code, -triangle(-res.value) + res.pvalue, 0)
      end
    end
  end
  -- cubic (tehtmi)
  -- (n){(({}[()])){({}[()])}{}}{}
  -- (n^3-3*n^2+8*n-6)/6
  -- (-6 + n*(8 + n*(-3 + n)))/6
  --[[ superceded by negative cubic because 
       it is the same cost of -ncubic(-n)
  if length - 28 >= 2 then
    for _, res in get_pushes(length - 28) do
      if res.value > 0 then
        local code = "{(({}[()])){({}[()])}{}}{}"
        local v = res.value + 1
        v = (-6 + v*(8 + v*(-3 + v)))//6
        register_push(res.prefix .. "(" .. res.suffix .. ")", code, v - res.value, res.pvalue + res.value)
        register_push(res.prefix, "(" .. res.suffix .. ")" .. code, v, res.pvalue)
        register_push("", res.prefix .. "(" .. res.suffix .. ")" .. code, v + res.pvalue, 0)
      end
    end
  end
  --]]
  -- negative cubic (tehtmi)
  -- (n){(({}())){({}())}{}}{}
  -- (n^3-3*n^2+8*n-6)/6
  -- (-6 + n*(8 + n*(-3 + n)))/6
  -- [[
  if length - 24 >= 2 then
    for _, res in get_pushes(length - 24) do
      if res.value < 0 then
        local code = "{(({}())){({}())}{}}{}"
        local v = -res.value + 1
        v = (-6 + v*(8 + v*(-3 + v)))//6
        v = -v
        register_push(res.prefix .. "(" .. res.suffix .. ")", code, v - res.value, res.pvalue + res.value)
        register_push(res.prefix, "(" .. res.suffix .. ")" .. code, v, res.pvalue)
        register_push("", res.prefix .. "(" .. res.suffix .. ")" .. code, v + res.pvalue, 0)
      end
    end
  end
  --]]
  -- polynomial (Wheat Wizard, modified by tehtmi)
  -- <(n)>{A({}[()])B}{} where A, B are ({})({})({})... repeated a, b times
  -- <(n)>                -- push n (without adding)
  --      {          }    -- repeat until top is zero
  --       A              -- top * a
  --        ({}[()])      -- top = top - 1; += top - 1
  --                B     -- (top - 1) * b
  --                  {}  -- pop 0
  -- triangular numbers are with a = b = 0
  -- from B and base:
  -- (n - 1) * (B + 1) * (n - 2) * (B + 1) * ...
  -- (B + 1) * (1 + ... + n - 1)
  -- (B + 1) * n * (n - 1) / 2
  -- from A:
  -- n * A + (n - 1) * A + ...
  -- A * (1 + ... n)
  -- A * (n + 1) * n / 2
  -- total: (B + 1) * n * (n - 1) / 2 + A * (n + 1) * n / 2
  --        [(A + B + 1) * n^2 + (A - B - 1) * n] / 2
  -- S := 4 * (A + B)
  -- [[
  if length - 18 >= 2 then
    for S = 4, length - 14, 4 do
      for _, res in get_pushes(length - 14 - S) do
        if res.value > 0 then
          for _, A in ipairs(poly_multipliers) do
            if A.l > S then
              break
            end
            for _, B in ipairs(poly_multipliers) do
              if A.l + B.l < S then
                -- continue
              elseif A.l + B.l > S then
                break
              else
                local a = A.m
                local b = B.m
                local logic = "{" .. A.s .. "({}[()])" .. B.s .. "}{}"
                local v = res.value
                v = ((a + b + 1) * v * v + (a - b - 1) * v) // 2
                register_push(res.prefix .. "(" .. res.suffix .. ")", logic, v, res.pvalue + res.value)
                register_push(res.prefix, "(" .. res.suffix .. ")" .. logic, v + res.value, res.pvalue)
                register_push("", res.prefix .. "(" .. res.suffix .. ")" .. logic, v + res.value + res.pvalue, 0)
              end
            end
          end
        end
      end
    end
  end
  --]]
  -- negative polynomial (tehtmi)
  -- <(n)>{A({}())B}{}
  -- [[
  if length - 16 >= 2 then
    for S = 4, length - 12, 4 do
      for _, res in get_pushes(length - 12 - S) do
        if res.value < 0 then
          for _, A in ipairs(poly_multipliers) do
            if A.l > S then
              break
            end
            for _, B in ipairs(poly_multipliers) do
              if A.l + B.l < S then
                -- continue
              elseif A.l + B.l > S then
                break
              else
                local a = A.m
                local b = B.m
                local logic = "{" .. A.s .. "({}())" .. B.s .. "}{}"
                local v = -res.value
                v = ((a + b + 1) * v * v + (a - b - 1) * v) // -2
                register_push(res.prefix .. "(" .. res.suffix .. ")", logic, v, res.pvalue + res.value)
                register_push(res.prefix, "(" .. res.suffix .. ")" .. logic, v + res.value, res.pvalue)
                register_push("", res.prefix .. "(" .. res.suffix .. ")" .. logic, v + res.value + res.pvalue, 0)
              end
            end
          end
        end
      end
    end
  end
  --]]
  -- addition
  -- [[
  if length >= 4 then
    for part1 = 4, length // 2, 2 do
      for _, res1 in get_pushes(part1) do
        for _, res2 in get_pushes(length - part1) do
          register_push(res2.prefix .. res1.prefix, res1.suffix .. res2.suffix, res1.value + res2.value, res1.pvalue + res2.pvalue)
        end
      end
    end
  end
  --]]
  -- pseudo-exponentiation (tehtmi)
  -- (n)<>(m){({}[()])<>(({}){})<>}{}<>{}
  -- (n)<>(m)                             -- push n and m on opposite stacks
  --         {                    }       -- sum and repeat
  --          ({}[()])                    -- top(m) - 1
  --                  <>(({}){})<>        -- n = 2*n; += n
  --                               {}     -- pop 0
  --                                 <>   -- swap to result
  --                                   {} -- pop and add n
  -- [[
  if length - 34 >= 4 then
    local subl = length - 34
    for part1 = 2, subl - 2, 2 do
      for _, res2 in get_pushes(part1) do
        local b = res2.value
        if b > 0 and b < 55 then -- overflow could be a problem, so bound...
          for _, res1 in get_pushes(subl - part1) do
            -- 2n + 4n + 8n + ... + (2^m)*n + 2^m * n
            -- n( 2 + 4 + 8 + .. 2^m + 2^m)
            -- n( 3 * 2^m - 2 )
            local a = res1.value
            local body = "(" .. res1.suffix .. ")<>" .. res2.prefix .. "(" .. res2.suffix .. "){({}[()])<>(({}){})<>}{}<>{}"
            local v = a * (3 * (1 << b) - 2) + b * (b - 1) // 2 + a + b + res2.pvalue
            register_push(res1.prefix, body, v, res1.pvalue)
            register_push("", res1.prefix .. body, v + res1.pvalue, 0)
          end
        end
      end
    end
  end
  --]]
end
--print(os.clock(), "seconds (startup)")
local start = os.clock()
for i = 2, k_max_len - 2, 2 do
  --print(i)
  process(i)
end
plen_cache = nil
local final = {}
for i = 1, k_limit do
  if pcache[i] ~= nil then
    final[i] = pcache[i].prefix .. "(" .. pcache[i].suffix .. ")"
  end
end
pcache = nil
-- hard coded to 10000 for ppcg test
local sieve = {}
for i = 1, 10000 do sieve[i] = true end
for i = 2, 10000 do
  for j = i * i, 10000, i do
    sieve[j] = false
  end
end
--print(os.clock() - start, "seconds (calculation)")
--local bf = require("execute2")
local count = 0
local sum = 0
local sum2 = 0
local maxlen = 0
local pcount = 0
for i = 1, k_limit do
  local res = final[i]
  final[i] = nil
  --print(i, #res, res)
  --local ev = res and bf.eval1(bf.compile(res)) or -1; assert( res == nil or ev == i, string.format("Failed %d %s %d", i, res or "", ev))
  if sieve[i] and i > 1000 then
    sum = #res + sum
    pcount = pcount + 1
  end
  if res then
    sum2 = #res + sum2
    maxlen = math.max(maxlen, #res)
    count = count + 1
  end
end
print("sum", sum)
--print("coverage", count / k_limit, "missing", k_limit - count)
--print("sum2", sum2)
--print("maxlen", maxlen)
assert(pcount == 1061)
与其他答案的想法类似,在后者中,已知有用的函数用于根据较简单数字的良好表示来构建较大数字。
一个区别是,我不是在解决具有较小数字的子问题,而是在解决具有较短表示形式的数字的子问题。我认为这使得利用负数以及处理以较大数字表示较小数字的情况更加优雅。
而且,尝试查找可以以一定大小表示的所有数字,而不是尝试尽可能短地表示特定数字,实际上简化了某些计算。与其反向处理公式以查看是否可以将其应用于数字,不如将公式向前处理并应用于每个数字。
另一个区别是,已知解决方案存储在两部分中-一个(可选)“前缀”和一个“后缀”(更像是一个后缀)。计算给定数字时,前缀的评估预计会被忽略-前缀仅包含用于设置要运行的后缀的代码(通常通过将一个或多个内容压入堆栈)。因此,给定前缀和后缀,可以使用将对应的数字压入堆栈prefix(suffix)。
此拆分基本上解决了与unpackWheat Wizard答案中的功能相同的问题。而不是<...>仅包装代码以稍后撤消,而是将这些代码简单地添加到前缀中。
在某些情况下,确实会对前缀进行评估(主要是针对伪幂运算),因此也会存储其估值。但是,这实际上并不会引起什么大问题,因为生成器并未尝试构造特定的数字。从理论上讲,这似乎意味着可能存在两段相同长度的代码,并生成相同数量的代码,由于具有不同的前缀值,因此在缓存中不会是多余的。不过,我并没有为此而烦恼,因为这似乎无关紧要(至少在此领域中如此)。
我想通过增加更多的情况来减少字节数是很容易的,但是目前我已经受够了。
我已经达到了1000000,但最多只能进行100000次健全性检查。
给定素数的输出粘贴框。
               
              
2n为4^n catalan(n)。