0253 solved.

0253-Meeting-Rooms-II/cpp-0253/CMakeLists.txt

@@ -0,0 +1,7 @@
+cmake_minimum_required(VERSION 3.5)
+project(cpp_0253)
+
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
+
+set(SOURCE_FILES main4.cpp)
+add_executable(cpp_0253 ${SOURCE_FILES})

0253-Meeting-Rooms-II/cpp-0253/main.cpp

@@ -0,0 +1,69 @@
+/// Source : https://leetcode.com/problems/meeting-rooms-ii/description/
+/// Author : liuyubobobo
+/// Time   : 2018-09-10
+
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+
+/// Simulation
+/// Time Complexity: O(n^2)
+/// Space Complexity: O(n)
+
+/// Definition for an interval.
+struct Interval {
+    int start;
+    int end;
+    Interval() : start(0), end(0) {}
+    Interval(int s, int e) : start(s), end(e) {}
+};
+
+class Solution {
+
+public:
+    int minMeetingRooms(vector<Interval>& intervals) {
+
+        sort(intervals.begin(), intervals.end(), cmpIntervals);
+
+        vector<Interval> rooms;
+        int sz = 0, res = 0;
+        for(const Interval& meeting: intervals){
+
+            for(Interval& room: rooms)
+                if(room.end != -1 && room.end <= meeting.start){
+                    room.start = room.end = -1;
+                    sz --;
+                }
+
+            bool ok = false;
+            for(Interval& room: rooms)
+                if(room.start == -1){
+                    room = meeting;
+                    ok = true;
+                    break;
+                }
+            if(!ok)
+                rooms.push_back(meeting);
+            sz ++;
+
+            res = max(res, sz);
+        }
+
+        return res;
+    }
+
+private:
+    static bool cmpIntervals(const Interval& i1, const Interval& i2){
+        if(i1.start != i2.start)
+            return i1.start < i2.start;
+        return i1.end < i2.end;
+    }
+};
+
+
+int main() {
+
+    return 0;
+}

0253-Meeting-Rooms-II/cpp-0253/main2.cpp

@@ -0,0 +1,67 @@
+/// Source : https://leetcode.com/problems/meeting-rooms-ii/description/
+/// Author : liuyubobobo
+/// Time   : 2018-09-10
+
+#include <iostream>
+#include <vector>
+#include <queue>
+
+using namespace std;
+
+
+/// Simulation
+/// Using Priority Queue
+///
+/// Time Complexity: O(nlogn)
+/// Space Complexity: O(n)
+
+/// Definition for an interval.
+struct Interval {
+    int start;
+    int end;
+    Interval() : start(0), end(0) {}
+    Interval(int s, int e) : start(s), end(e) {}
+};
+
+class Solution {
+
+private:
+    class CompareInterval{
+    public:
+        bool operator()(const Interval& a, const Interval& b){
+            return a.end > b.end;
+        }
+    };
+
+public:
+    int minMeetingRooms(vector<Interval>& intervals) {
+
+        sort(intervals.begin(), intervals.end(), cmpIntervals);
+
+        priority_queue<Interval, vector<Interval>, CompareInterval> rooms;
+        int res = 0;
+        for(const Interval& meeting: intervals){
+
+            while(!rooms.empty() && rooms.top().end <= meeting.start)
+                rooms.pop();
+
+            rooms.push(meeting);
+            res = max(res, (int)rooms.size());
+        }
+
+        return res;
+    }
+
+private:
+    static bool cmpIntervals(const Interval& i1, const Interval& i2){
+        if(i1.start != i2.start)
+            return i1.start < i2.start;
+        return i1.end < i2.end;
+    }
+};
+
+
+int main() {
+
+    return 0;
+}

0253-Meeting-Rooms-II/cpp-0253/main3.cpp

@@ -0,0 +1,58 @@
+/// Source : https://leetcode.com/problems/meeting-rooms-ii/description/
+/// Author : liuyubobobo
+/// Time   : 2018-09-10
+
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+
+/// Two Pointers
+/// Sorting start time and end time seperately.
+///
+/// Time Complexity: O(nlogn)
+/// Space Complexity: O(n)
+
+/// Definition for an interval.
+struct Interval {
+    int start;
+    int end;
+    Interval() : start(0), end(0) {}
+    Interval(int s, int e) : start(s), end(e) {}
+};
+
+class Solution {
+public:
+    int minMeetingRooms(vector<Interval>& intervals) {
+
+        if(intervals.size() == 0)
+            return 0;
+
+        vector<int> starts, ends;
+        for(const Interval& interval: intervals){
+            starts.push_back(interval.start);
+            ends.push_back(interval.end);
+        }
+        sort(starts.begin(), starts.end());
+        sort(ends.begin(), ends.end());
+
+
+        int res = 1, sz = 1;
+        int end_index = 0;
+        for(int start_index = 1; start_index < starts.size(); start_index ++){
+            while(end_index < ends.size() && ends[end_index] <= starts[start_index])
+                end_index ++, sz --;
+            sz ++;
+            res = max(res, sz);
+        }
+
+        return res;
+    }
+};
+
+
+int main() {
+
+    return 0;
+}

0253-Meeting-Rooms-II/cpp-0253/main4.cpp

@@ -0,0 +1,55 @@
+/// Source : https://leetcode.com/problems/meeting-rooms-ii/description/
+/// Author : liuyubobobo
+/// Time   : 2018-09-10
+
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+
+/// Dealing with start time and end time seperately
+/// make start time and end time in a pair structure
+/// and deal with them in one single vector:)
+///
+/// Time Complexity: O(nlogn)
+/// Space Complexity: O(n)
+
+/// Definition for an interval.
+struct Interval {
+    int start;
+    int end;
+    Interval() : start(0), end(0) {}
+    Interval(int s, int e) : start(s), end(e) {}
+};
+
+class Solution {
+public:
+    int minMeetingRooms(vector<Interval>& intervals) {
+
+        vector<pair<int, char>> timepoints;
+        for(const Interval& interval: intervals){
+            timepoints.push_back(make_pair(interval.start, 's'));
+            timepoints.push_back(make_pair(interval.end, 'e'));
+        }
+        sort(timepoints.begin(), timepoints.end());
+
+        int res = 0;
+        int cur = 0;
+        for(const pair<int, char>& p: timepoints)
+            if(p.second == 's'){
+                cur ++;
+                res = max(res, cur);
+            }
+            else
+                cur --;
+
+        return res;
+    }
+};
+
+
+int main() {
+
+    return 0;
+}

readme.md

@@ -230,7 +230,7 @@ email: [[email protected]](mailto:[email protected])
 | 250 | [Count Univalue Subtrees](https://leetcode.com/problems/count-univalue-subtrees/description/) | [无] | [C++](0250-Count-Univalue-Subtrees/cpp-0250/) | | |
 | | | | | | |
 | 252 | [Meeting Rooms](https://leetcode.com/problems/meeting-rooms/description/) | [solution](https://leetcode.com/problems/meeting-rooms/solution/) | [C++](0252-Meeting-Rooms/cpp-0252/) | | |
-| | | | | | |
+| 253 | [Meeting Rooms II](https://leetcode.com/problems/meeting-rooms-ii/description/) | [solution](https://leetcode.com/problems/meeting-rooms-ii/solution/) | [C++](0253-Meeting-Rooms-II/cpp-0253/) | | |
 | 254 | [Factor Combinations](https://leetcode.com/problems/factor-combinations/description/) | [无] | [C++](0254-Factor-Combinations/cpp-0254/) | | |
 | | | | | | |
 | 257 | [Binary Tree Paths](https://leetcode.com/problems/binary-tree-paths/description/) | [缺：非递归算法] | [C++](0257-Binary-Tree-Paths/cpp-0257/) | [Java](0257-Binary-Tree-Paths/java-0257/src/) | |