Initial data commit

Task/N-queens-problem/UNIX-Shell/n-queens-problem.sh

@@ -0,0 +1,78 @@
+#!/bin/bash
+
+# variable declaration
+typeset -i BoardSize=8
+typeset -i p=0
+typeset -i total=0
+typeset -i board
+
+# initialization
+function init
+{
+    for (( i=0;i<$BoardSize;i++ ))
+    do
+        (( board[$i]=-1 ))
+    done
+}
+
+# check if queen can be placed
+function place
+{
+        typeset -i flag=1
+        for (( i=0;i<$1;i++ ))
+        do
+                if [[ (${board[$i]}-${board[$1]} -eq ${i}-${1}) || (${board[$i]}-${board[$1]} -eq ${1}-${i}) || (${board[$i]} -eq ${board[$1]}) ]]
+                then
+                        (( flag=0 ))
+                fi
+        done
+        [[ $flag -eq 0 ]]
+        return $?
+}
+
+# print the result
+function out
+{
+        printf "Problem of queen %d:%d\n" $BoardSize $total
+}
+
+# free the variables
+function depose
+{
+    unset p
+    unset total
+    unset board
+    unset BoardSize
+}
+
+# back tracing
+function work
+{
+    while [[ $p -gt -1 ]]
+        do
+        (( board[$p]++ ))
+        if  [[ ${board[$p]} -ge ${BoardSize} ]]
+        then  # back tracing
+            (( p-- ))
+        else  # try next position
+            place $p
+            if [[ $? -eq 1 ]]
+            then
+                (( p++ ))
+                if [[ $p -ge ${BoardSize} ]]
+                then
+                    (( total++ ))
+                    (( p-- ))
+                else
+                    (( board[$p]=-1 ))
+                fi
+            fi
+        fi
+    done
+}
+
+# entry
+init
+work
+out
+depose