Add 991

Author: trung-hn

Readme.md

@@ -234,6 +234,7 @@
 | 983 | Minimum Cost For Tickets | Medium | O(365) | O(365) | LRU Cache, Dynamic Programming | | |
 | 986 | Interval List Intersections | Medium | O(N + M) | O(1) | Two Pointers | | |
 | 987 | Vertical Order Traversal of a Binary Tree | Medium | O(NlogN) | O(N) | Hash Table, Tree | | |
+| 991 | Broken Calculator | Medium | O(logN) | O(1) | Math, Greedy | | |
 | 993 | Cousins in Binary Tree | Easy | O(N) | O(H) | Trees, Recursion | | |
 | 994 | Rotting Oranges | Medium | O(N^2) | O(N) | Trees, Recursion | | |
 | 1004 | Max Consecutive Ones III | Medium | O(N) | O(1) | Sliding Window, Two Pointers | | |

src/991.broken-calculator.py

@@ -0,0 +1,28 @@
+#
+# @lc app=leetcode id=991 lang=python3
+#
+# [991] Broken Calculator
+#
+
+# @lc code=start
+# TAGS: Math, Greedy
+class Solution:
+    # 20 ms, 99%. Time: O(logN). Space: O(1). 
+    def brokenCalc(self, X: int, Y: int) -> int:
+        if X >= Y: return X - Y
+        
+        cnt = 0
+        while X < Y:
+            X *= 2
+            cnt += 1
+            
+        diff = X - Y
+        for i in range(cnt, -1, -1):
+            d, diff = divmod(diff, 2**i)
+            cnt += d
+        return cnt
+            
+                
+        
+# @lc code=end
+

testcases/991

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