Update 数组的排列组合.js

数组的排列组合.js

@@ -1,22 +1,45 @@
-var arr = [1, 2, 3]
-var _arr = []
-function getArrange(arr, selectNum, selectedArr) {
-    if (selectNum === 1) {
-        for (var i = 0; i < arr.length; i++) {
-            var newSelectedArr = selectedArr.slice();
-            newSelectedArr.push(arr[i]);
-            _arr.push(newSelectedArr);
-        }
-    } else {
-        selectNum -= 1; //剩余选择的减一
-        for (var i = 0; i < arr.length; i++) {
-            var newSelectedArr = selectedArr.slice();
-            var newArr = arr.slice();
-            newSelectedArr.push(arr[i]);
-            newArr.splice(i, 1); //删除push进去的那一个
-            getArrange(newArr, selectNum, newSelectedArr);
+// 全排列
+function Permutations (target, size, origin) {
+    var _arr = []
+    function getArrange(target, nums, ret) {
+        if (nums === 1) {
+            for (var i = 0; i < target.length; i++) {
+                var tmp = ret.slice();
+                tmp.push(target[i]);
+                _arr.push(tmp);
+            }
+        } else {
+            nums -= 1;
+            for (var i = 0; i < target.length; i++) {
+                var tmp = ret.slice();
+                var newTarget = target.slice();
+                tmp.push(target[i]);
+                newTarget.splice(i, 1);
+                getArrange(newTarget, nums, tmp);
+            }
         }
     }
+    getArrange(target, size, origin);
     return _arr;
 }
-getArrange(arr, 2, [])
+Permutations([1, 2, 3], 2, [])
+
+// 排列组合
+function Permutations (arr, size) {
+  var ret = [];
+
+  function getRet(origin, target, size) {
+    if (size === 0) {
+      ret[ret.length] = origin;
+      return;
+    }
+    for (var i = 0; i <= target.length - size; i++) {
+      var tmp = origin.slice();
+      tmp.push(target[i]);
+      getRet(tmp, target.slice(i + 1), size - 1);
+    }
+  }
+  getRet([], arr, size);
+  return ret;
+}
+Permutations([1, 2, 3, 4], 3)