Merge branch 'main' into feat/DP_problem

Author: SjxSubham

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);
+    }
+};

3350. Adjacent Increasing Subarrays Detection II.cpp

@@ -0,0 +1,55 @@
+#include <iostream>
+using namespace std;
+/*
+APPROACH:
+Use an array to track lengths of increasing streaks, then apply binary search
+to find the largest k for which two adjacent increasing subarrays exist.
+*/
+bool check(int *inc, int n, int k)
+{
+    for (int end1 = k - 1; end1 + k < n; end1++)
+    {
+        if (inc[end1] >= k && inc[end1 + k] >= k)
+        {
+            return true;
+        }
+    }
+    return false;
+}
+
+int maxIncreasingSubarrays(int *nums, int numsSize)
+{
+    int n = numsSize;
+    int inc[n];
+    for (int i = 0; i < n; i++)
+        inc[i] = 1;
+
+    // Build the increasing streak lengths
+    for (int i = 1; i < n; i++)
+    {
+        if (nums[i] > nums[i - 1])
+        {
+            inc[i] = inc[i - 1] + 1;
+        }
+    }
+
+    int L = 1, R = n / 2;
+    int ans = 0;
+
+    // Binary search for max k
+    while (L <= R)
+    {
+        int mid = L + (R - L) / 2;
+        if (check(inc, n, mid))
+        {
+            ans = mid; // mid works, try bigger k
+            L = mid + 1;
+        }
+        else
+        {
+            R = mid - 1; // mid too big, try smaller k
+        }
+    }
+
+    return ans;
+}

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];
+    }
+};