Create set-intersection-size-at-least-two.cpp

Author: kamyu104

C++/set-intersection-size-at-least-two.cpp

@@ -0,0 +1,28 @@
+// Time:  O(nlogn)
+// Space: O(n)
+
+// greedy solution
+class Solution {
+public:
+    int intersectionSizeTwo(vector<vector<int>>& intervals) {
+        sort(intervals.begin(), intervals.end(),
+             [](const vector<int>& a, const vector<int>& b) {
+                 return (a[0] != b[0]) ? (a[0] < b[0]) : (b[1] < a[1]);
+             });
+        vector<int> cnts(intervals.size(), 2);
+        int result = 0;
+        while (!intervals.empty()) {
+            auto start = intervals.back()[0]; intervals.pop_back();
+            auto cnt = cnts.back(); cnts.pop_back();
+            for (int s = start; s < start + cnt; ++s) {
+                for (int i = 0; i < intervals.size(); ++i) {
+                    if (cnts[i] && s <= intervals[i][1]) {
+                        --cnts[i];
+                    }
+                }
+            }
+            result += cnt;
+        }
+        return result;
+    }
+};