permutation

lightningtgc · lightningtgc · commit 515b41dd8c34 · 2015-03-06T01:27:29.000+08:00
diff --git a/common.md b/common.md
@@ -125,3 +125,41 @@ function countNumber(n){
   return count;
 }
 ```
+
+### 8.穷举排列(permutation)
+
+[see](http://www.lifelaf.com/blog/?p=1228)
+
+穷举一个数组中各个元素的排列
+
+策略
+
+减而治之、递归
+
+```js
+/**
+ * Created by cshao on 12/23/14.
+ */
+
+function getPermutation(arr) {
+  if (arr.length == 1) {
+    return [arr];
+  }
+
+  var permutation = [];
+  for (var i=0; i<arr.length; i++) {
+    var firstEle = arr[i];
+    var arrClone = arr.slice(0);
+    arrClone.splice(i, 1);
+    var childPermutation = getPermutation(arrClone);
+    for (var j=0; j<childPermutation.length; j++) {
+      childPermutation[j].unshift(firstEle);
+    }
+    permutation = permutation.concat(childPermutation);
+  }
+  return permutation;
+}
+
+var permutation = getPermutation(['a','b','c']);
+console.dir(permutation);
+```
