Create maximum-possible-number-by-binary-concatenation.cpp

Author: kamyu104

C++/maximum-possible-number-by-binary-concatenation.cpp

@@ -0,0 +1,59 @@
+// Time:  O(n * logr * logn)
+// Space: O(nlogr)
+
+// sort
+class Solution {
+public:
+    int maxGoodNumber(vector<int>& nums) {
+        const auto& to_binary = [](int x) {
+            string result;
+            for (; x; x >>= 1) {
+                result.push_back(x & 1 ? '1' : '0');
+            }
+            reverse(begin(result), end(result));
+            return result;
+        };
+
+        vector<string> bins(size(nums));
+        for (int i = 0; i < size(nums); ++i) {
+            bins[i] = to_binary(nums[i]);
+        }
+        sort(begin(bins), end(bins), [](const auto& a, const auto& b) {
+            return (a + b) > (b + a);
+        });
+        string result;
+        for (const auto& x : bins) {
+            result += x;
+        }
+        return stoi(result, nullptr, 2);
+    }
+};
+
+// Time:  O(n! * nlogr)
+// Space: O(nlogr)
+// brute force
+class Solution2 {
+public:
+    int maxGoodNumber(vector<int>& nums) {
+        const auto& to_binary = [](int x) {
+            string result;
+            for (; x; x >>= 1) {
+                result.push_back(x & 1 ? '1' : '0');
+            }
+            reverse(begin(result), end(result));
+            return result;
+        };
+
+        vector<int> idxs(size(nums));
+        iota(begin(idxs), end(idxs), 0);
+        int result = 0;
+        do {
+            string curr;
+            for (const auto& i : idxs) {
+                curr += to_binary(nums[i]);
+            }
+            result = max(result, stoi(curr, nullptr, 2));
+        } while (next_permutation(begin(idxs), end(idxs)));
+        return result;
+    }
+};