Update random-pick-with-blacklist.cpp

Author: kamyu104

C++/random-pick-with-blacklist.cpp

@@ -44,43 +44,26 @@ class Solution {
 class Solution2 {
 public:
     Solution(int N, vector<int> blacklist) :
-        n_(N - blacklist.size()) {
-            
-        sort(blacklist.begin(), blacklist.end());
-        int prev = 0, count = 0;
-        for (const auto& black : blacklist) {
-            if (prev != black) {
-                intervals_.push_back({prev, black, count});
-                count += black - prev;
-            }
-            prev = black + 1;
-        }
-        intervals_.push_back({prev, N, count});
-    }
-    
+        n_(N - blacklist.size()),
+        blacklist_(blacklist) {
+		sort(blacklist_.begin(), blacklist_.end());
+	}
+
     int pick() {
         int index = rand() % n_;
-        int left = 0, right = intervals_.size() - 1;
+        int left = 0, right = blacklist_.size() - 1;
         while (left <= right) {
-            int mid = left + (right - left) / 2;
-            const auto& cur = intervals_[mid];
-            if (index < cur.accu_count + cur.right - cur.left) {
+            auto mid = left + (right - left) / 2;
+            if (index + mid < blacklist_[mid]) {
                 right = mid - 1;
             } else {
                 left = mid + 1;
             }
         }
-        Interval cur = intervals_[left];
-        return cur.left + index - cur.accu_count;
+        return index + left;
     }
 
-private:
-    struct Interval {
-        int left;
-        int right;
-        int accu_count;
-    };
-        
+private:        
     int n_;
-    vector<Interval> intervals_;
+    vector<int> blacklist_;
 };