922

Author: ProHiryu

code/922.sort-array-by-parity-ii.py

@@ -0,0 +1,30 @@
+#
+# @lc app=leetcode id=922 lang=python3
+#
+# [922] Sort Array By Parity II
+#
+
+# @lc code=start
+class Solution:
+    def sortArrayByParityII(self, a: List[int]) -> List[int]:
+        i = 0 # pointer for even misplaced
+        j = 1 # pointer for odd misplaced
+        sz = len(a)
+        
+        # invariant: for every misplaced odd there is misplaced even
+        # since there is just enough space for odds and evens
+
+        while i < sz and j < sz:
+            if a[i] % 2 == 0:
+                i += 2
+            elif a[j] % 2 == 1:
+                j += 2
+            else:
+                # a[i] % 2 == 1 AND a[j] % 2 == 0
+                a[i],a[j] = a[j],a[i]
+                i += 2
+                j += 2
+
+        return a
+# @lc code=end
+