DP-1 Complete

Sample.java

@@ -5,3 +5,72 @@
 
 
 // Your code here along with comments explaining your approach
+// https://leetcode.com/problems/coin-change/description/
+// Time Complexity : O(m*n) where m is number of coins and n is amount
+// Space complexity : O(m*n)
+// Did this code successfully run on Leetcode : yes
+class Solution {
+    public int coinChange(int[] coins, int amount) {
+        int[][] dp = new int[coins.length+1][amount+1];
+        int re = helper(coins,0,amount,dp);
+        if(re==99999) return -1;
+        return re;
+    }
+    int helper(int[] coins,int idx,int amount,int[][] dp){
+        // base
+        if(amount==0) return 0;
+        if(amount<0) return 99999;
+        if(idx==coins.length){
+            return 99999;
+        }
+        if(dp[idx][amount]!=0) return dp[idx][amount];
+        // logic
+        // pick the current idx value
+       int case2 = helper(coins,idx+1,amount,dp);
+       int case1 = 1+helper(coins,idx,amount-coins[idx],dp);
+
+       // not pick the current idx value
+       dp[idx][amount] =  Math.min(case1,case2);
+       return Math.min(case1,case2);
+    }
+}
+// https://leetcode.com/problems/house-robber/description/
+//  Time Complexity : O(n) where n is number of houses
+// Space complexity : O(n)
+// Did this code successfully run on Leetcode : yes
+class Solution {
+    public int rob(int[] nums) {
+        if(nums.length==1) return nums[0];
+        int[] dp = new int[nums.length];
+        Arrays.fill(dp,-1);
+        return helper(nums,0,dp);
+    }
+    int helper(int[] nums,int idx,int[] dp){
+        // base case
+        if(idx>=nums.length) return 0;
+        if(dp[idx]!=-1) return dp[idx];
+        // logic
+        // pick house at index idx 
+        int case1 = nums[idx]+helper(nums,idx+2,dp);
+        // dont pick the house at index idx
+        int case2 = helper(nums,idx+1,dp);
+        dp[idx] = Math.max(case1,case2);
+        return Math.max(case1,case2);
+    }
+}
+//  Time Complexity : O(n) where n is number of houses
+// Space complexity : O(n)
+// Did this code successfully run on Leetcode : yes
+class Solution {
+    public int rob(int[] nums) {
+       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 = curr;
+          curr = Math.max(curr,nums[i]+prev);
+          prev = temp;
+       }
+       return curr;
+    }
+}