Create minimum-deletions-to-make-string-k-special.py

Author: kamyu104

Python/minimum-deletions-to-make-string-k-special.py

@@ -0,0 +1,63 @@
+# Time:  O(n + 26)
+# Space: O(n + 26)
+
+# freq table, counting sort, two pointers
+class Solution(object):
+    def minimumDeletions(self, word, k):
+        """
+        :type word: str
+        :type k: int
+        :rtype: int
+        """
+        def counting_sort(arr, key=lambda x:x, reverse=False):  # Time: O(n), Space: O(n)
+            count = [0]*(max(arr, key=key)+1)
+            for x in arr:
+                count[key(x)] += 1
+            for i in xrange(1, len(count)):
+                count[i] += count[i-1]
+            result = [0]*len(arr)
+            if not reverse:
+                for x in reversed(arr):  # stable sort
+                    count[key(x)] -= 1
+                    result[count[key(x)]] = x
+            else:
+                for x in arr:  # stable sort
+                    count[key(x)] -= 1
+                    result[count[key(x)]] = x
+                result.reverse()
+            return result
+    
+        cnt = [0]*26
+        for x in word:
+            cnt[ord(x)-ord('a')] += 1
+        arr = counting_sort([x for x in cnt if x])
+        result = float("inf")
+        right = prefix = 0
+        suffix = len(word)
+        prev = -1
+        for left in xrange(len(arr)):
+            if left+1 < len(arr) and arr[left+1] == arr[left]:
+                continue
+            while right < len(arr) and arr[right] <= arr[left]+k:
+                suffix -= arr[right]
+                right += 1
+            result = min(result, prefix+(suffix-(arr[left]+k)*(len(arr)-right)))
+            prefix += arr[left]*(left-prev)
+            prev = left
+        return result
+
+
+# Time:  O(n + 26^2)
+# Space: O(26)
+# freq table
+class Solution2(object):
+    def minimumDeletions(self, word, k):
+        """
+        :type word: str
+        :type k: int
+        :rtype: int
+        """
+        cnt = [0]*26
+        for x in word:
+            cnt[ord(x)-ord('a')] += 1
+        return min(sum(y if y < x else max(y-(x+k), 0) for y in cnt if y) for x in cnt if x)