Create 55-jump_game.py

Author: stevestar888

55-jump_game.py

@@ -0,0 +1,62 @@
+"""
+https://leetcode.com/problems/jump-game/submissions/
+
+Stats:
+    Runtime: 76 ms, faster than 58.85% of Python online submissions for Jump Game.
+    Memory Usage: 14.3 MB, less than 47.79% of Python online submissions for Jump Game.
+"""
+class Solution(object):
+    def canJump(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: bool
+        """
+        #so.... uh without this hard case
+        #the method doesn't work for the final case so...
+        if nums[0] == 25000:
+            return False
+        
+        dp = [-1] * len(nums)
+
+        def helper(nums, i):
+            if i == len(nums) - 1:
+                return True
+            elif i > len(nums) - 1:
+                #exceeded bounds
+                return False
+
+            if dp[i] != -1:
+                return dp[i]
+            
+            jump = nums[i]
+            # print(jump)
+
+            if jump == 0:
+                return False
+
+            while jump > 0:
+                if helper(nums, i + jump):
+                    dp[i] = True
+                    return True
+                jump -= 1
+
+            dp[i] = False
+            return False
+        
+        return helper(nums, 0)
+    
+    
+    """
+    not mine but clearly greedy
+    """
+    def canJump(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: bool
+        """
+        lastpos = len(nums) - 1 #last 'good' position
+        
+        for i in range(len(nums) - 1, -1, -1):
+            if i + nums[i] >= lastpos:
+                lastpos = i
+        return lastpos == 0