Strange Printer

heoh/leetcode-664.py

@@ -0,0 +1,76 @@
+class Solution:
+    def strangePrinter(self, s: str) -> int:
+        # aaaaabbbbbbccccccaaaaaa -> abca
+        ss = s[0]
+        for c in s[1:]:
+            if c != ss[-1]:
+                ss += c
+        s = ss
+
+        cost = {}
+        for i in range(len(s)):
+            for j in range(len(s) + 1):
+                if i < j:
+                    cost[i, j] = self.strangePrinter2(s[i:j])
+
+        cache = {}
+        def div_and_conq(i, j):
+            if (i, j) in cache:
+                return cache[i, j]
+
+            best = cost[i, j]
+            for m in range(i+1, j):
+                cur_cost = div_and_conq(i, m) + div_and_conq(m, j)
+                best = min(best, cur_cost)
+
+            cache[i, j] = best
+            return cache[i, j]
+
+        return div_and_conq(0, len(s))
+
+    def strangePrinter2(self, s: str) -> int:
+        scope_right_stack = []
+
+        print_cnt = 0
+        paper = '_' * len(s)
+
+        scope_left = 0
+        scope_right = len(s)
+        scope_right_stack.append(scope_right)
+
+        for i in range(len(s)):
+            if s[i] == paper[i]:
+                continue
+
+            left_char = s[i]
+            scope_left = i
+            while scope_right <= scope_left:
+                scope_right_stack.pop()
+                scope_right = scope_right_stack[-1]
+
+            scope_right = s.rindex(left_char, scope_left, scope_right)
+            scope_right_stack.append(scope_right)
+
+            paper = self.print(paper, scope_left, scope_right, left_char)
+            print_cnt += 1
+
+        return print_cnt
+
+
+
+    def print(self, paper, left, right, char):
+        return paper[:left] + char * (right - left + 1) + paper[right+1:]
+
+
+def main():
+    assert Solution().strangePrinter('tbgtgb') == 4
+    assert Solution().strangePrinter('abc') == 3
+    assert Solution().strangePrinter('aaabbb') == 2
+    assert Solution().strangePrinter('aba') == 2
+    assert Solution().strangePrinter('aabbaabbaa') == 3
+    assert Solution().strangePrinter('aabbaabbccaabbccbbaabbccaa') == 8
+    assert Solution().strangePrinter('baacdddaaddaaaaccbddbcabdaabdbbcdcbbbacbddcabcaaa') == 19
+
+
+if __name__ == '__main__':
+    main()