Update wiggle-sort-ii.cpp

lifei023 · Jan 1, 2016 · 7546b9e · 7546b9e
1 parent b664834
commit 7546b9e
Showing 1 changed file with 27 additions and 9 deletions.
diff --git a/C++/wiggle-sort-ii.cpp b/C++/wiggle-sort-ii.cpp
@@ -1,12 +1,12 @@
 // Time:  O(n) ~ O(n^2)
 // Space: O(1)
 
-// Dutch flag sorting with virtual index solution.
+// Dutch flag sorting with virtual index solution. (44ms)
 class Solution {
 public:
     void wiggleSort(vector<int>& nums) {
         int mid = (nums.size() - 1) / 2;
-        nth_element(nums.begin(), nums.begin() + mid, nums.end());
+        nth_element(nums.begin(), nums.begin() + mid, nums.end());  // O(n) ~ O(n^2)
         reversedDutchFlagSortWithVI(nums, nums[mid]);
     }
 
@@ -27,20 +27,19 @@ class Solution {
 
 // Time:  O(n) ~ O(n^2)
 // Space: O(n)
-// Dutch flag sorting solution.
+// Dutch flag sorting solution. (64ms)
 class Solution2 {
 public:
     void wiggleSort(vector<int>& nums) {
-        const int n = nums.size();
-        int mid = (n - 1) / 2;
-        nth_element(nums.begin(), nums.begin() + mid, nums.end());
+        int mid = (nums.size() - 1) / 2;
+        nth_element(nums.begin(), nums.begin() + mid, nums.end());  // O(n) ~ O(n^2)
         dutchFlagSort(nums, nums[mid]);
 
-        vector<int> res(n);
-        for (int i = 0, smallEnd = mid;  i < n; i += 2, --smallEnd) {
+        vector<int> res(nums.size());
+        for (int i = 0, smallEnd = mid;  i < nums.size(); i += 2, --smallEnd) {
             res[i] = nums[smallEnd];
         }
-        for (int i = 1, largeEnd = n - 1; i < n; i += 2, --largeEnd) {
+        for (int i = 1, largeEnd = nums.size() - 1; i < nums.size(); i += 2, --largeEnd) {
             res[i] = nums[largeEnd];
         }
         nums = res;
@@ -58,3 +57,22 @@ class Solution2 {
         }
     }
 };
+
+// Time:  O(nlogn)
+// Space: O(n)
+// Sorting and reorder solution. (64ms)
+class Solution3 {
+public:
+    void wiggleSort(vector<int>& nums) {
+        int mid = (nums.size() - 1) / 2;
+        sort(nums.begin(), nums.end());
+        vector<int> res(nums.size());
+        for (int i = 0, smallEnd = mid;  i < nums.size(); i += 2, --smallEnd) {
+            res[i] = nums[smallEnd];
+        }
+        for (int i = 1, largeEnd = nums.size() - 1; i < nums.size(); i += 2, --largeEnd) {
+            res[i] = nums[largeEnd];
+        }
+        nums = res;
+    }
+};