leetcode 55

python

Author: kyle8998

README.md

@@ -51,6 +51,7 @@ Personal Practice Set - Doing One a Day (sometimes) in a Variety of Languages (M
 | 49 | Medium     | [Group Anagrams](leetcode/49-Medium-Group-Anagrams/problem.md)                               | [Python](leetcode/49-Medium-Group-Anagrams/answer.py)             |
 | 53 | Easy       | [Maximum Subarray](leetcode/53-Easy-Maximum-Subarray/problem.md)                             | [Java](leetcode/53-Easy-Maximum-Subarray/answer.java)             |
 | 54 | Medium     | [Spiral Matrix](leetcode/54-Medium-Spiral-Matrix/problem.md)                                 | [Python](leetcode/54-Medium-Spiral-Matrix/answer.py)              |
+| 55 | Medium     | [Jump Game](leetcode/55-Medium-Jump-Game/problem.md)                                         | [Python](leetcode/55-Medium-Jump-Game/answer.py)                  |
 | 56 | Medium     | [Merge Intervals](leetcode/56-Medium-Merge-Intervals/problem.md)                             | [Python](leetcode/56-Medium-Merge-Intervals/answer.py)            |
 | 58 | Easy       | [Length of Last Word](leetcode/58-Easy-Length-Of-Last-Word/problem.md)                       | [Python](leetcode/58-Easy-Length-Of-Last-Word/answer.py)          |
 | 62 | Medium     | [Unique Paths](leetcode/62-Medium-Unique-Paths/problem.md)                                   | [Python](leetcode/62-Medium-Unique-Paths/answer.py)               |

leetcode/55-Medium-Jump-Game/answer.py

@@ -0,0 +1,49 @@
+#!/usr/bin/python3
+
+#------------------------------------------------------------------------------
+# Brute Force O(n^2)
+#------------------------------------------------------------------------------
+
+class Solution(object):
+    def canJump(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: bool
+        """
+        if len(nums) <= 1:
+            return True
+        valid = [len(nums)-1]
+        done = []
+        while valid:
+            curr = valid.pop(0)
+            if curr not in done:
+                done.append(curr)
+                valid += self.getList(nums, curr)
+                if 0 in valid:
+                    return True
+        return False
+    
+    def getList(self, nums, idx):
+        result = []
+        for i in range(0, idx):
+            if nums[i] >= (idx - i):
+                result.append(i)
+        return result
+        
+#------------------------------------------------------------------------------
+# Optimized O(n)
+#------------------------------------------------------------------------------
+
+class Solution(object):
+    def canJump(self, nums):
+        if not nums:
+            return False
+        curr = len(nums) - 1
+        for i in range(len(nums)-1, -1, -1):
+            if nums[i] >= curr - i:
+                curr = i
+        return True if not curr else False
+        
+
+#------------------------------------------------------------------------------
+#Testing

leetcode/55-Medium-Jump-Game/problem.md

@@ -0,0 +1,24 @@
+# Problem 55: Jump Game
+
+#### Difficulty: Medium
+
+#### Problem
+
+Given an array of non-negative integers, you are initially positioned at the first index of the array.
+
+Each element in the array represents your maximum jump length at that position.
+
+Determine if you are able to reach the last index.
+
+#### Example
+
+<pre>
+Input: [2,3,1,1,4]
+Output: true
+Explanation: Jump 1 step from index 0 to 1, then 3 steps to the last index.
+
+Input: [3,2,1,0,4]
+Output: false
+Explanation: You will always arrive at index 3 no matter what. Its maximum
+             jump length is 0, which makes it impossible to reach the last index.
+</pre>