completed DP-1

CoinChange.java

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+// Time Complexity : O(N)
+// Space Complexity : O(N)
+// Did this code successfully run on Leetcode : yes
+// Any problem you faced while coding this :
+
+
+// Your code here along with comments explaining your approach
+class Solution {
+    public int coinChange(int[] coins, int amount) {
+        // 2D DP
+        // // 0 to coins is row
+        // // 0 to amount is col
+        // int[][] dp = new int[coins.length+1][amount+1];
+        // // set first row (coin 0) to max value - coz we are considering min
+        // // we can consider amount+1 as max value
+        // for(int i = 1; i <= amount; i++)
+        // {
+        //     dp[0][i] = amount+1;
+        // }
+
+        // for(int i = 1; i <= coins.length; i++)
+        // {
+        //     for(int j = 0; j <= amount; j++)
+        //     {
+        //         if(coins[i-1] > j)
+        //         {
+        //             // as value as the grid above
+        //             dp[i][j] = dp[i-1][j];
+        //         }
+        //         else
+        //         {
+        //             dp[i][j] = Math.min(dp[i-1][j], 1+ dp[i][j - coins[i-1]]);
+        //         }
+        //     }
+        // }
+
+        // if(dp[coins.length][amount] >= amount + 1)
+        // {
+        //     return -1;
+        // }
+        // return dp[coins.length][amount];
+
+        // 1D DP
+        int dp[] = new int[amount+1];
+        for(int i = 1; i <= amount; i++)
+        {
+            dp[i] = amount+1;
+        }
+        for(int i = 1; i <= coins.length; i++)
+        {
+            for(int j = 0; j <= amount; j++)
+            {
+                if(coins[i - 1] > j)
+                {
+                    dp[j] = dp[j];
+                }
+                else
+                {
+                    dp[j] = Math.min(dp[j], dp[j- coins[i-1]] + 1);
+                }
+            }
+        }
+        if(dp[amount] >= amount+1) return -1;
+        return dp[amount];
+    }
+}
+

HouseRobber.java

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+// Time Complexity : O(N)
+// Space Complexity : O(1)
+// Did this code successfully run on Leetcode :
+// Any problem you faced while coding this :
+
+
+// Your code here along with comments explaining your approach
+
+class Solution {
+    public int rob(int[] nums) {
+        // 1D array
+        // if(nums.length == 1) return nums[0];
+
+        // int dp[] = new int[nums.length];
+        // dp[0] = nums[0];
+        // dp[1] = Math.max(nums[0], nums[1]);
+        // for(int i = 2; i < nums.length; i++)
+        // {
+        //     dp[i] = Math.max(nums[i] + dp[i-2], dp[i-1]);
+        // }
+        // return dp[nums.length - 1];
+
+        // two variables
+        if(nums.length == 1) return nums[0];
+        int prev = nums[0];
+        int curr = Math.max(nums[0], nums[1]);
+
+        for(int i = 2; i < nums.length; i++)
+        {
+            int temp = Math.max(curr, prev+nums[i]);
+            prev = curr;
+            curr = temp;
+        }
+
+        return curr;
+    }
+}