Data commit

Task/Permutations/R/permutations-1.r

@@ -0,0 +1,35 @@
+next.perm <- function(a) {
+  n <- length(a)
+  i <- n
+  while (i > 1 && a[i - 1] >= a[i]) i <- i - 1
+  if (i == 1) {
+    NULL
+  } else {
+    j <- i
+    k <- n
+    while (j < k) {
+      s <- a[j]
+      a[j] <- a[k]
+      a[k] <- s
+      j <- j + 1
+      k <- k - 1
+    }
+    s <- a[i - 1]
+    j <- i
+    while (a[j] <= s) j <- j + 1
+    a[i - 1] <- a[j]
+    a[j] <- s
+    a
+  }
+}
+
+perm <- function(n) {
+  e <- NULL
+  a <- 1:n
+  repeat {
+    e <- cbind(e, a)
+    a <- next.perm(a)
+    if (is.null(a)) break
+  }
+  unname(e)
+}

Task/Permutations/R/permutations-2.r

@@ -0,0 +1,5 @@
+> perm(3)
+     [,1] [,2] [,3] [,4] [,5] [,6]
+[1,]    1    1    2    2    3    3
+[2,]    2    3    1    3    1    2
+[3,]    3    2    3    1    2    1

Task/Permutations/R/permutations-3.r

@@ -0,0 +1,11 @@
+# list of the vectors by inserting x in s at position 0...end.
+linsert <- function(x,s) lapply(0:length(s), function(k) append(s,x,k))
+
+# list of all permutations of 1:n
+perm <- function(n){
+    if (n == 1) list(1)
+    else unlist(lapply(perm(n-1), function(s) linsert(n,s)),
+                recursive = F)}
+
+# permutations of a vector s
+permutation <- function(s) lapply(perm(length(s)), function(i) s[i])

Task/Permutations/R/permutations-4.r

@@ -0,0 +1,18 @@
+> permutation(letters[1:3])
+[[1]]
+[1] "c" "b" "a"
+
+[[2]]
+[1] "b" "c" "a"
+
+[[3]]
+[1] "b" "a" "c"
+
+[[4]]
+[1] "c" "a" "b"
+
+[[5]]
+[1] "a" "c" "b"
+
+[[6]]
+[1] "a" "b" "c"