DP-2 Complete Please Review

coinChange2.cpp

@@ -0,0 +1,54 @@
+/* ################################################## Recursive Solution ################################################## */
+
+class Solution {
+public:
+    int helper(int amount, vector<int>& coins, int idx)
+    {
+        if (idx >= coins.size() || amount < 0) {
+            return 0;
+        }
+
+        if (amount == 0) {
+            return 1;
+        }
+
+        int result = 0;
+        result += helper(amount - coins[idx], coins, idx);
+        result += helper(amount, coins, idx + 1);
+
+        return result;
+    }
+    int change(int amount, vector<int>& coins)
+    {
+        return helper(amount, coins, 0);
+    }
+};
+
+
+/* ################################################## DP Solution ################################################## */
+
+
+class Solution {
+public:
+    void helper(vector<unsigned>& dp)
+    {
+        for (int i = 1; i < dp.size(); i++) {
+            dp[i] = 0;
+        }
+
+        dp[0] = 1;
+    }
+    int change(int amount, vector<int>& coins)
+    {
+        vector<unsigned>dp(amount + 1, 0);
+        helper(dp);
+
+        for (int i = 1; i <= coins.size(); i++) {
+            for (int j = coins[i - 1]; j <= amount; j++) {
+                dp[j] += dp[j - coins[i - 1]];
+            }
+        }
+
+        return dp[amount];
+    }
+};

paintHouse.cpp

@@ -0,0 +1,59 @@
+/* ################################################## Recursive Solution ################################################## */
+
+class Solution {
+public:
+    int helper (vector<vector<int>>& costs, int i, int col)
+    {
+        if (i == costs.size()) {
+            return 0;
+        }
+
+        if (col == 0) {
+            return costs[i][col] + min(helper(costs, i + 1, 1),helper(costs, i + 1, 2)); 
+        }
+
+        if (col == 1) {
+            return costs[i][col] + min(helper(costs, i + 1, 0),helper(costs, i + 1, 2));
+        }
+
+        if (col == 2) {
+            return costs[i][col] + min(helper(costs, i + 1, 1),helper(costs, i + 1, 0));
+        }
+
+        return 0;
+    }
+    int minCost(vector<vector<int>>& costs) 
+    {
+        return min(helper(costs, 0, 0), min(helper(costs, 0, 1), helper(costs, 0, 2)));
+    }
+};
+
+
+/* ################################################## DP Solution ################################################## */
+
+class Solution {
+public:
+    int minCost(vector<vector<int>>& costs) 
+    {
+        int dp[3];
+
+        int n = costs.size();
+        dp[0] = costs[n - 1][0];
+        dp[1] = costs[n - 1][1];
+        dp[2] = costs[n - 1][2];
+
+        for (int i = n - 2; i >= 0; i--) {
+            int temp0 = dp[0];
+            dp[0] = costs[i][0] + min(dp[1], dp[2]);
+
+            int temp1 = dp[1];
+            dp[1] = costs[i][1] + min(temp0, dp[2]);
+
+            dp[2] = costs[i][2] + min(temp1, temp0);
+        }
+
+        return min(dp[0], min(dp[1], dp[2]));
+    }
+};
+
+