96.Unique Binary Search Trees

135. Candy.cpp

@@ -0,0 +1,24 @@
+class Solution {
+public:
+    int candy(vector<int>& ratings) {
+        int n = ratings.size();
+        vector<int> count(n, 1);  // Step 1: Initialize with 1
+
+        // Step 2: Left to Right
+        for (int i = 1; i < n; i++) {
+            if (ratings[i] > ratings[i - 1]) {
+                count[i] = count[i - 1] + 1;
+            }
+        }
+
+        // Step 3: Right to Left
+        for (int i = n - 2; i >= 0; i--) {
+            if (ratings[i] > ratings[i + 1]) {
+                count[i] = max(count[i], count[i + 1] + 1);
+            }
+        }
+
+        // Step 4: Total candies
+        return accumulate(count.begin(), count.end(), 0);
+    }
+};

188. Best Time to Buy and Sell Stock IV.cpp

@@ -0,0 +1,27 @@
+class Solution {
+public:
+    vector<vector<vector<int>>> dp;
+
+    int profit(vector<int>& prices, int i, int isBuy, int k) {
+        if (i == prices.size() || k == 0) return 0;
+
+        if (dp[i][isBuy][k] != -1) return dp[i][isBuy][k];
+
+        int a, b;
+        if (isBuy) {
+            a = profit(prices, i + 1, 1, k);
+            b = profit(prices, i + 1, 0, k) - prices[i];
+        } else {
+            a = profit(prices, i + 1, 0, k);
+            b = profit(prices, i + 1, 1, k - 1) + prices[i];
+        }
+
+        return dp[i][isBuy][k] = max(a, b);
+    }
+
+    int maxProfit(int k, vector<int>& prices) {
+        int n = prices.size();
+        dp = vector<vector<vector<int>>>(n, vector<vector<int>>(2, vector<int>(k + 1, -1)));
+        return profit(prices, 0, 1, k);
+    }
+};

96. Unique Binary Search Trees.cpp

@@ -0,0 +1,11 @@
+class Solution {
+public:
+    int dp[20]{};
+    int numTrees(int n) {
+        if(n <= 1) return 1;
+        if(dp[n]) return dp[n];
+        for(int i = 1; i <= n; i++) 
+            dp[n] += numTrees(i-1) * numTrees(n-i);
+        return dp[n];
+    }
+};