Data commit

Task/Balanced-ternary/Lua/balanced-ternary.lua

@@ -0,0 +1,146 @@
+function to_bt(n)
+    local d = { '0', '+', '-' }
+    local v = { 0, 1, -1 }
+
+    local b = ""
+
+    while n ~= 0 do
+        local r = n % 3
+        if r < 0 then
+            r = r + 3
+        end
+
+        b = b .. d[r + 1]
+
+        n = n - v[r + 1]
+        n = math.floor(n / 3)
+    end
+
+    return b:reverse()
+end
+
+function from_bt(s)
+    local n = 0
+
+    for i=1,s:len() do
+        local c = s:sub(i,i)
+        n = n * 3
+        if c == '+' then
+            n = n + 1
+        elseif c == '-' then
+            n = n - 1
+        end
+    end
+
+    return n
+end
+
+function last_char(s)
+    return s:sub(-1,-1)
+end
+
+function add(b1,b2)
+    local out = "oops"
+    if b1 ~= "" and b2 ~= "" then
+        local d = ""
+
+        local L1 = last_char(b1)
+        local c1 = b1:sub(1,-2)
+        local L2 = last_char(b2)
+        local c2 = b2:sub(1,-2)
+        if L2 < L1 then
+            L2, L1 = L1, L2
+        end
+
+        if L1 == '-' then
+            if L2 == '0' then
+                d = "-"
+            end
+            if L2 == '-' then
+                d = "+-"
+            end
+        elseif L1 == '+' then
+            if L2 == '0' then
+                d = "+"
+            elseif L2 == '-' then
+                d = "0"
+            elseif L2 == '+' then
+                d = "-+"
+            end
+        elseif L1 == '0' then
+            if L2 == '0' then
+                d = "0"
+            end
+        end
+
+        local ob1 = add(c1,d:sub(2,2))
+        local ob2 = add(ob1,c2)
+
+        out = ob2 .. d:sub(1,1)
+    elseif b1 ~= "" then
+        out = b1
+    elseif b2 ~= "" then
+        out = b2
+    else
+        out = ""
+    end
+
+    return out
+end
+
+function unary_minus(b)
+    local out = ""
+
+    for i=1, b:len() do
+        local c = b:sub(i,i)
+        if c == '-' then
+            out = out .. '+'
+        elseif c == '+' then
+            out = out .. '-'
+        else
+            out = out .. c
+        end
+    end
+
+    return out
+end
+
+function subtract(b1,b2)
+    return add(b1, unary_minus(b2))
+end
+
+function mult(b1,b2)
+    local r = "0"
+    local c1 = b1
+    local c2 = b2:reverse()
+
+    for i=1,c2:len() do
+        local c = c2:sub(i,i)
+        if c == '+' then
+            r = add(r, c1)
+        elseif c == '-' then
+            r = subtract(r, c1)
+        end
+        c1 = c1 .. '0'
+    end
+
+    while r:sub(1,1) == '0' do
+        r = r:sub(2)
+    end
+
+    return r
+end
+
+function main()
+    local a = "+-0++0+"
+    local b = to_bt(-436)
+    local c = "+-++-"
+    local d = mult(a, subtract(b, c))
+
+    print(string.format("      a: %14s %10d", a, from_bt(a)))
+    print(string.format("      b: %14s %10d", b, from_bt(b)))
+    print(string.format("      c: %14s %10d", c, from_bt(c)))
+    print(string.format("a*(b-c): %14s %10d", d, from_bt(d)))
+end
+
+main()