add sort-characters-by-frequency.py

Author: lightmen

python/hash-table/sort-characters-by-frequency.py

@@ -0,0 +1,24 @@
+class Solution(object):
+    def frequencySort(self, s):
+        """
+        :type s: str
+        :rtype: str
+        """
+        d = {}
+        l = []
+        for c in s:
+            d[c] = d.get(c, 0) + 1
+
+        for c in d:
+            index = 0
+            while index < len(l):
+                if d[l[index]] < d[c]:
+                    break
+                index += 1
+            l.insert(index, c)
+
+        res = ""
+        for c in l:
+            res += c * d[c]
+
+        return res