Implement Coin change And House Robber

CoinChange.java

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+// Time Complexity : O(mxn)
+// Space Complexity : O(amount)
+// Did this code successfully run on Leetcode : yes
+// Any problem you faced while coding this :no 
+
+
+// Your code here along with comments explaining your approach
+
+//Using the DP we will set the for each coin we will asign hingher value than amount  and 
+//find the minimum coins for amount j is either the old answer, or using this coin plus 
+// the best answer for the remaining amount.
+
+class CoinChange{
+    public int coinChange(int[] coins, int amount) {
+
+          int n = coins.length;
+          int []dp = new int[amount+1];
+
+          for(int i = 1; i <= amount; i++){
+               dp[i] = amount+1;
+          }
+
+          for(int i = 1; i <= n; i++){
+            for(int j = 1; j <= amount; j++){
+                if(coins[i-1] <= j){
+                   dp[j] = Math.min(dp[j], dp[j-coins[i-1]]);
+                }
+            }
+          }
+
+        if(dp[amount] > amount){
+            return -1;
+        }
+
+        return dp[amount];
+    }
+}

HouseRobber.java

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+public class HouseRobber {
+    public int rob(int[] nums) {
+
+         int n = nums.length;
+
+         if(n == 1) return nums[0]; 
+         int prev = nums[0];
+         int curr = Math.min(prev, nums[1]);
+
+         for(int i = 2; i < n; i++){
+             int temp =curr;
+             curr = Math.max(prev+nums[i], curr);
+             prev = curr;
+         }
+
+        return curr;
+
+    }
+}