test18.pins24

# Test 18 - Combination of k numbers that sum up to n
# x1 + x2 + ... + xk = n
# a <= k <= b

# Constraints:
# a <= b <= n
# a > 1

var a = 2
var b = 4
var n = 5

# Prints possible combinations
# Returns number of combinations
fun sum(i, total) =
    let
        var result = 0
        var st = 1
        var j = 1
    in
        if total > n || i > b then
            result = 0
        else
            if total == n && i >= a then
                putint(digits^),
                while j < i do
                    putstr(" + \00"),
                    putint((digits + 4 * j)^),
                    j = j + 1
                end,
                putstr(" = \00"),
                putint(total),
                putstr("\n\00"),
                result = 1
            end,

            while st < n do
                (digits + 4 * i)^ = st,
                result = result + sum(i + 1, total + st),
                st = st + 1
            end
        end,
        result
    end

var digits = 0
fun main() =
    digits = new(4 * n),
    sum(0, 0)

fun putint(int)
fun putstr(straddr)
fun new(size)