Data update

Task/Permutations-by-swapping/Dart/permutations-by-swapping.dart

@@ -0,0 +1,61 @@
+void main() {
+  List<int> array = List.generate(4, (i) => i);
+  HeapsAlgorithm algorithm = HeapsAlgorithm();
+  algorithm.recursive(array);
+  print('');
+  algorithm.loop(array);
+}
+
+class HeapsAlgorithm {
+  void recursive(List array) {
+    _recursive(array, array.length, true);
+  }
+
+  void _recursive(List array, int n, bool plus) {
+    if (n == 1) {
+      _output(array, plus);
+    } else {
+      for (int i = 0; i < n; i++) {
+        _recursive(array, n - 1, i == 0);
+        _swap(array, n % 2 == 0 ? i : 0, n - 1);
+      }
+    }
+  }
+
+  void _output(List array, bool plus) {
+    print(array.toString() + (plus ? ' +1' : ' -1'));
+  }
+
+  void _swap(List array, int a, int b) {
+    var temp = array[a];
+    array[a] = array[b];
+    array[b] = temp;
+  }
+
+  void loop(List array) {
+    _loop(array, array.length);
+  }
+
+  void _loop(List array, int n) {
+    List<int> c = List.filled(n, 0);
+    _output(array, true);
+    bool plus = false;
+    int i = 0;
+    while (i < n) {
+      if (c[i] < i) {
+        if (i % 2 == 0) {
+          _swap(array, 0, i);
+        } else {
+          _swap(array, c[i], i);
+        }
+        _output(array, plus);
+        plus = !plus;
+        c[i]++;
+        i = 0;
+      } else {
+        c[i] = 0;
+        i++;
+      }
+    }
+  }
+}

Task/Permutations-by-swapping/EasyLang/permutations-by-swapping.easy

@@ -0,0 +1,20 @@
+# Heap's Algorithm
+sig = 1
+proc generate k . ar[] .
+   if k = 1
+      print ar[] & "  " & sig
+      sig = -sig
+      return
+   .
+   generate k - 1 ar[]
+   for i to k - 1
+      if k mod 2 = 0
+         swap ar[i] ar[k]
+      else
+         swap ar[1] ar[k]
+      .
+      generate k - 1 ar[]
+   .
+.
+ar[] = [ 1 2 3 ]
+generate len ar[] ar[]