Data commit

Task/N-queens-problem/R/n-queens-problem-1.r

@@ -0,0 +1,28 @@
+queens <- function(n) {
+  a <- seq(n)
+  u <- rep(T, 2 * n - 1)
+  v <- rep(T, 2 * n - 1)
+  m <- NULL
+  aux <- function(i) {
+    if (i > n) {
+      m <<- cbind(m, a)
+    } else {
+      for (j in seq(i, n)) {
+        k <- a[[j]]
+        p <- i - k + n
+        q <- i + k - 1
+        if (u[[p]] && v[[q]]) {
+          u[[p]] <<- v[[q]] <<- F
+          a[[j]] <<- a[[i]]
+          a[[i]] <<- k
+          aux(i + 1)
+          u[[p]] <<- v[[q]] <<- T
+          a[[i]] <<- a[[j]]
+          a[[j]] <<- k
+        }
+      }
+    }
+  }
+  aux(1)
+  m
+}

Task/N-queens-problem/R/n-queens-problem-2.r

@@ -0,0 +1,3 @@
+library(Matrix)
+a <- queens(8)
+as(a[, 1], "pMatrix")

Task/N-queens-problem/R/n-queens-problem-3.r

@@ -0,0 +1 @@
+sapply(4:12, function(n) ncol(queens(n)))