78.Subsets

2561.RearrangingFruits.cpp

@@ -0,0 +1,31 @@
+
+#include <bits/stdc++.h>
+using namespace std;
+
+class Solution {
+public:
+    vector<int> rearrangeFruits(vector<int>& fruits) {
+
+        unordered_map<int, int> freq;
+        for (int fruit : fruits) freq[fruit]++;
+
+
+        priority_queue<pair<int,int>> pq;
+        for (auto &p : freq) pq.push({p.second, p.first});
+
+        vector<int> result;
+        pair<int,int> prev = {-1, -1}; // last placed fruit
+
+        while (!pq.empty()) {
+            auto cur = pq.top(); pq.pop();
+            result.push_back(cur.second);
+            cur.first--;
+
+            if (prev.first > 0) pq.push(prev);
+            prev = cur;
+        }
+
+        return result;
+    }
+};
+

78.Subsets.cpp

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+// Subsets using Backtracking (DFS)
+// -------------------------------
+// Intuition: Each element can be either taken or not taken → 2^n subsets
+// Approach: Use DFS recursion with backtracking to explore both choices
+// Time Complexity: O(n * 2^n)
+// Space Complexity: O(n) recursion stack (excluding output)
+
+#include <bits/stdc++.h>
+using namespace std;
+
+class Solution {
+public:
+    void dfs(int idx, vector<int>& nums, vector<int>& path, vector<vector<int>>& ans) {
+        if (idx == (int)nums.size()) { 
+            ans.push_back(path); 
+            return; 
+        }
+        // Choice 1: not take nums[idx]
+        dfs(idx + 1, nums, path, ans);
+
+        // Choice 2: take nums[idx]
+        path.push_back(nums[idx]);
+        dfs(idx + 1, nums, path, ans);
+
+        path.pop_back(); // backtrack (undo choice)
+    }
+
+    vector<vector<int>> subsets(vector<int>& nums) {
+        vector<vector<int>> ans;  
+        vector<int> path;        
+        dfs(0, nums, path, ans);  
+        return ans;
+    }
+};