- Added guest contributions by Laurent Rosenfeld.

10 files changed, 198 insertions, 0 deletions

diff --git a/challenge-109/laurent-rosenfeld/c/ch-2.c b/challenge-109/laurent-rosenfeld/c/ch-2.c
new file mode 100644
index 0000000000..85022d6dd9
--- /dev/null
+++ b/challenge-109/laurent-rosenfeld/c/ch-2.c
@@ -0,0 +1,33 @@
+#include <stdio.h>
+
+int check_squares (int p[]) {
+    int sum = p[0] + p[1];
+    return ( p[1] + p[2] + p[3] == sum &&
+        p[3] + p[4] + p[5] == sum &&
+        p[5] + p[6] == sum);
+}
+
+void swap (int a[], int m, int n) {
+    int temp = a[m];
+    a[m] = a[n];
+    a[n] = temp;
+}
+
+int main() {
+    int in[7] = {7, 6, 5, 4, 3, 2, 1}; # values must be in descending order
+    int i, j;
+    int fact = 5040;        //factorial 7
+    while (fact--) {
+        if (check_squares(in)) {
+            for (int i = 0; i < 6; i++) printf("%d ", in[i]);
+            printf("%d\n", in[6]);
+        }
+        i = 1;
+        while (in[i] > in[i-1]) i++;
+        j = 0;
+        while (in[j] < in[i]) j++;
+        swap(in, i, j);
+        i--;
+        for (j = 0; j < i; i--, j++) swap(in, i, j);
+    }
+}
diff --git a/challenge-109/laurent-rosenfeld/d/ch-2.d b/challenge-109/laurent-rosenfeld/d/ch-2.d
new file mode 100644
index 0000000000..8ce0553755
--- /dev/null
+++ b/challenge-109/laurent-rosenfeld/d/ch-2.d
@@ -0,0 +1,14 @@
+bool check_squares (int [] p) {
+    int sum = p[0] + p[1];
+    return ( p[1] + p[2] + p[3] == sum &&
+        p[3] + p[4] + p[5] == sum &&
+        p[5] + p[6] == sum);
+}
+
+void main() {
+    import std.stdio, std.algorithm;
+    auto items = [1, 2, 3, 4, 5, 6, 7];
+    do
+        if (check_squares(items)) items.writeln;
+    while (items.nextPermutation);
+}
diff --git a/challenge-109/laurent-rosenfeld/go/ch-2.go b/challenge-109/laurent-rosenfeld/go/ch-2.go
new file mode 100644
index 0000000000..2af4e8f721
--- /dev/null
+++ b/challenge-109/laurent-rosenfeld/go/ch-2.go
@@ -0,0 +1,37 @@
+package main
+
+import "fmt"
+
+func check_squares ( p[] int) bool {
+    var sum = p[0] + p[1]
+    return ( p[1] + p[2] + p[3] == sum &&
+        p[3] + p[4] + p[5] == sum &&
+        p[5] + p[6] == sum)
+}
+
+func main() {
+    var in = []int{1, 2, 3, 4, 5, 6, 7}
+    var max = len(in) - 1
+    var i, j int
+    for c := 1; c < 5040; c++ { // 7! = 5040
+        i = max - 1
+        j = max
+        for in[i] > in[i+1] {
+            i--
+        }
+        for in[j] < in[i] {
+            j--
+        }
+        in[i], in[j] = in[j], in[i]
+        j = max
+        i += 1
+        for i < j {
+            in[i], in[j] = in[j], in[i]
+            i++
+            j--
+        }
+        if check_squares(in) {
+            fmt.Println(in)
+        }
+    }
+}
diff --git a/challenge-109/laurent-rosenfeld/julia/ch-2.julia b/challenge-109/laurent-rosenfeld/julia/ch-2.julia
new file mode 100644
index 0000000000..d60cea1b4d
--- /dev/null
+++ b/challenge-109/laurent-rosenfeld/julia/ch-2.julia
@@ -0,0 +1,25 @@
+function check_squares(p)
+    ∑ = p[1] + p[2]
+    return (p[2] + p[3] + p[4] == ∑ &&
+        p[4] + p[5] + p[6] == ∑ &&
+        p[6] + p[7] == ∑)
+end
+
+function permute(k, in)  # Heap's algorithm
+    if (k == 1)
+        if (check_squares(in)) println(in) end
+        # println(in)
+    else
+        permute(k - 1, in)
+        for i = 1:(k-1)
+            if (k % 2 == 0)
+                in[i], in[k] = in[k], in[i]
+            else
+                in[1], in[k] = in[k], in[1]
+            end
+            permute(k - 1, in)
+        end
+    end
+end
+
+permute(7, [1, 2, 3, 4, 5, 6, 7])
diff --git a/challenge-109/laurent-rosenfeld/kotlin/ch-2.kt b/challenge-109/laurent-rosenfeld/kotlin/ch-2.kt
new file mode 100644
index 0000000000..a24a2d1f28
--- /dev/null
+++ b/challenge-109/laurent-rosenfeld/kotlin/ch-2.kt
@@ -0,0 +1,28 @@
+fun <T> permute(input: List<T>): List<List<T>> {
+    if (input.size == 1) return listOf(input)
+    val perms = mutableListOf<List<T>>()
+    val toInsert = input[0]
+    for (perm in permute(input.drop(1))) {
+        for (i in 0..perm.size) {
+            val newPerm = perm.toMutableList()
+            newPerm.add(i, toInsert)
+            perms.add(newPerm)
+        }
+    }
+    return perms
+}
+
+fun check_squares(p: List<Int>): Boolean  {
+    val sum = p[0] + p[1]
+    return ( p[1] + p[2] + p[3] == sum &&
+             p[3] + p[4] + p[5] == sum &&
+             p[5] + p[6] == sum )
+}
+
+fun main(args: Array<String>) {
+    val input = listOf(1, 2, 3, 4, 5, 6, 7)
+    val perms = permute(input)
+    for (perm in perms) {
+        if (check_squares(perm)) println(perm)
+    }
+}
diff --git a/challenge-109/laurent-rosenfeld/lua/ch-2.lua b/challenge-109/laurent-rosenfeld/lua/ch-2.lua
new file mode 100644
index 0000000000..e972de6a62
--- /dev/null
+++ b/challenge-109/laurent-rosenfeld/lua/ch-2.lua
@@ -0,0 +1,20 @@
+local function check_square (p)
+    sum = p[1] + p[2]
+    return p[2] + p[3] + p[4] == sum and
+        p[4] + p[5] + p[6] == sum and
+        p[6] + p[7] == sum
+end
+
+local function permute(perm, n)
+    if n == 0  and check_square(perm) then
+        print( table.concat(perm, ' ') )
+    else
+        for i = 1, n do
+            perm[i], perm[n] = perm[n], perm[i]
+            permute(perm, n - 1)
+            perm[i], perm[n] = perm[n], perm[i]
+        end
+    end
+end
+
+permute({1,2,3,4,5,6,7}, 7)
diff --git a/challenge-109/laurent-rosenfeld/nim/ch-2.nim b/challenge-109/laurent-rosenfeld/nim/ch-2.nim
new file mode 100644
index 0000000000..129ac8a3ce
--- /dev/null
+++ b/challenge-109/laurent-rosenfeld/nim/ch-2.nim
@@ -0,0 +1,12 @@
+import algorithm
+
+proc check_squares (p: array[0..6, int]) : bool =
+    var sum = p[0] + p[1]
+    return ( p[1] + p[2] + p[3] == sum and
+      p[3] + p[4] + p[5] == sum and p[5] + p[6] == sum )
+
+
+var input = [1, 2, 3, 4, 5, 6, 7] # List has to start sorted
+while input.nextPermutation():
+  if check_squares(input):
+    echo input
diff --git a/challenge-109/laurent-rosenfeld/python/ch-2.py b/challenge-109/laurent-rosenfeld/python/ch-2.py
new file mode 100644
index 0000000000..95138e89c6
--- /dev/null
+++ b/challenge-109/laurent-rosenfeld/python/ch-2.py
@@ -0,0 +1,6 @@
+import itertools
+
+input = range(1, 8)  # 1 to 7
+for p in itertools.permutations(input):
+    if sum(p[0:2]) == sum(p[1:4]) == sum(p[3:6]) == sum(p[5:7]):
+        print (perm)
diff --git a/challenge-109/laurent-rosenfeld/ruby/ch-2.rb b/challenge-109/laurent-rosenfeld/ruby/ch-2.rb
new file mode 100644
index 0000000000..0a7fc1d4ba
--- /dev/null
+++ b/challenge-109/laurent-rosenfeld/ruby/ch-2.rb
@@ -0,0 +1,9 @@
+input = [1, 2, 3, 4, 5, 6, 7]
+for p in input.permutation
+    sum = p[0] + p[1]
+    if p[1] + p[2] + p[3] == sum and
+       p[3] + p[4] + p[5] == sum and
+       p[5] + p[6] == sum then
+        puts p.join(" ")
+    end
+end
diff --git a/challenge-109/laurent-rosenfeld/scala/ch-2.scala b/challenge-109/laurent-rosenfeld/scala/ch-2.scala
new file mode 100644
index 0000000000..f033cde350
--- /dev/null
+++ b/challenge-109/laurent-rosenfeld/scala/ch-2.scala
@@ -0,0 +1,14 @@
+object fourSquares extends App {
+  val in = (1 to 7).toList
+  for (perm <- in.permutations) {
+    val sum = perm.slice(0, 2).sum;
+        // In Scala, slice(0, 2) returns items 0 and 1
+    if (
+      perm.slice(1, 4).sum == sum &&
+      perm.slice(3, 6).sum == sum &&
+      perm.slice(5, 7).sum == sum
+    ) {
+      println(perm.mkString(" "))
+    }
+  }
+}