Completed DP-1

problem1.py

@@ -0,0 +1,44 @@
+class Solution:
+    def coinChange(self, coins: List[int], amount: int) -> int:
+        # memo={}
+        # def helper(index,total):
+        #     if (index,total) in memo:
+        #         return memo[(index,total)]
+        #     if total==amount:
+        #         return 0
+        #     if index>=len(coins) or total>amount:
+        #         return float('inf')
+
+        #     take = 1+ helper(index,total+coins[index])
+        #     skip = helper(index+1, total)
+        #     memo[(index,total)] = min(take,skip)
+        #     return memo[(index,total)]
+
+        # result = helper(0,0)
+        # return result if result!=float('inf') else -1
+
+
+        # Inititlie the dp array with 0's with one extra row and one extra column
+        dp = [[0]*(amount+1) for i in range(len(coins)+1)]
+
+        # Initialize the first row with max value as we can not make up those amount with 0 coin
+        for i in range(1,amount+1):
+            dp[0][i]=float('inf')
+
+        # Starting iteration for the 1st coin
+        for c in range(1,len(coins)+1):
+            for amt in range(1,amount+1):
+                # If we can make that amount with the given coin
+                if amt-coins[c-1]>=0:
+                    # It has to be the minimum of not chosing that coin which is present above
+                    # and chosing the coin, if we chose that see the value in the sub problem with the amount-coin
+                    dp[c][amt] = min(dp[c-1][amt],1+dp[c][amt-coins[c-1]])
+                else:
+                    #chose the row above
+                    dp[c][amt]=dp[c-1][amt]
+        # Check the last row and column of our dp table as this is where we have all the coins available and the amount
+        if dp[len(coins)][amount]!=float('inf'):
+             return dp[len(coins)][amount]
+        else:
+             return -1
+

problem2.py

@@ -0,0 +1,24 @@
+class Solution:
+    def rob(self, nums: List[int]) -> int:
+        # memo={}
+        # def helper(index,total):
+        #     if (index,total) in memo:
+        #         return memo[(index,total)]
+        #     if index>=len(nums):
+        #         return total
+        #     rob= helper(index+2,total+nums[index])
+        #     skip= helper(index+1, total)
+        #     memo[(index,total)]= max(rob,skip)
+        #     return memo[(index,total)]
+        # return helper(0,0)
+
+        n=len(nums)
+        # Taking an extra 0 for the ease of calculation
+        dp = [0]*(n+1)
+        dp[1]=nums[0]
+        for i in range(2,n+1):
+            # Either chose the current house and add it to the total of previous houses u robbed until now
+            # or dont rob so the total would be max until the prev house
+            dp[i]=max(dp[i-1],dp[i-2]+nums[i-1])
+        return dp[n]
+