Prob-1 & 2 solutions added

CoinChange.java

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+/*
+Author: Akhilesh Borgaonkar
+Problem: LC 322. Coin Change (DP-1)
+Approach: Using Dynamic Programming approach here to find the pattern of repeating sub-problems. 
+Time Complexity: O(m*n) where m is number of coins and n is amount
+Space complexity: O(1) constant
+LC verified
+*/
+
+class Solution {
+    public int coinChange(int[] coins, int amount) {
+        int[][] dp = new int[coins.length+1][amount+1];
+        int r = dp.length;
+        int c = dp[0].length;
+
+        for(int i=0; i<r; i++)
+            dp[i][0]=0;
+
+        for(int j=1; j<c; j++)
+            dp[0][j]=99999;
+
+        for(int i=1; i<r; i++){
+            for(int j=1; j<c; 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);
+            }
+        }
+        int result = dp[coins.length][amount];
+        if(result >= 99999)
+            return -1;
+        return result;
+    }
+}

HouseRobber.java

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+/*
+Author: Akhilesh Borgaonkar
+Problem: LC 198. House Robber (DP-1)
+Approach: Using Dynamic programming approach to find the pattern of repeating sub-problems. Further optimized it by using just 2 variables to store
+    previous problem results.
+Time Complexity: O(n) where n is number of elements in array.
+Space complexity: O(1) constant.
+LC Verified.
+*/
+
+class Solution {
+    public int rob(int[] nums) {
+        int chosen=0, notChosen=0;
+
+        for(int i=0; i<nums.length; i++){               
+            int temp = chosen;                  
+            chosen = notChosen + nums[i];             
+            notChosen = Math.max(temp, notChosen);
+        }
+
+        return Math.max(chosen, notChosen);
+    }
+}