Completed DP -1

Completed problems super30admin#21 & super30admin#22

Problem1.java

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+// Time Complexity : O(nXm) we loop through all numbers in nums and amount
+// Space Complexity : O(nXm) size of dp array.
+// Did this code successfully run on Leetcode : Yes
+// Any problem you faced while coding this : No
+
+public class Problem1 {
+
+    public int coinChange(int[] coins, int amount) {
+        if(coins.length == 0 || coins == null) return -1;
+
+        int[][] dp = new int[coins.length+1][amount+1];
+        for(int i = 0; i <= amount; i++){
+            dp[0][i] = amount+1;
+        }
+
+        for(int i = 1; i < coins.length+1; i++){
+            for(int j = 1; j < amount+1; j++){
+                if(j < coins[i-1]){
+                    dp[i][j] = dp[i-1][j];
+                }else{
+                    dp[i][j] = Math.min(dp[i-1][j], dp[i][j - coins[i-1]] + 1);
+                }
+            }
+        }
+        return dp[coins.length][amount] < amount + 1 ? dp[coins.length][amount] : -1;
+
+    }
+}

Problem2.java

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+// Time Complexity : O(n) we loop through all numbers in nums
+// Space Complexity : O(n) size of dp array. 
+// Did this code successfully run on Leetcode : Yes
+// Any problem you faced while coding this : No
+
+public class Problem2 {
+    public int rob(int[] nums) {
+        if(nums == null || nums.length == 0) return 0;
+
+        int length = nums.length;
+        int[] dp = new int[length + 1];
+
+        //base case
+        dp[length] = 0;
+        dp[length - 1] = nums[nums.length - 1];
+
+        for(int i = nums.length - 2; i >= 0; i--){
+            dp[i] = Math.max(dp[i+1], dp[i+2] + nums[i]);
+        }
+
+        return dp[0];
+    }
+}