Add combination computation and merge functions

Both functions manipulate arrays, the first one computes the
permutations of various lengths, the second one merges the second array
into the missing values in the first one.

Author: rouanth

solver.js

@@ -202,6 +202,47 @@ function partition_split_idx (A, B) {
 	return null;
 }
 
+function combinations (n, kmin, kmax) {
+	if (kmax < 0 || n < kmin) {
+		return [];
+	}
+
+	if (n === 0) {
+		return [[]];
+	}
+
+	if (n === 1) {
+		var res = [];
+		if (kmax > 0) {
+			res.push([1]);
+		}
+		if (kmin <= 0) {
+			res.push([0]);
+		}
+		console.log(res);
+		return res;
+	}
+
+	var combsPlus = combinations (n-1, kmin-1, kmax-1);
+	var combsMin  = combinations (n-1, kmin,   kmax);
+
+	combsPlus.map(function (el) { el.splice(0, 0, 1); return el; });
+	combsMin.map( function (el) { el.splice(0, 0, 0); return el; });
+        return combsPlus.concat(combsMin);
+}
+
+function merge (arr1, arr2) {
+	var s = arr1.slice();
+	var lp = 0;
+	for (var i = 0; i < arr2.length; ++i) {
+		while (lp in s) {
+			++lp;
+		}
+		s[lp] = arr2[i];
+	}
+	return s;
+}
+
 /* Find all possible solutions for A * X = B assuming that both a_ij and x_i
  * are in {true, false}.
  *