Feat: 435. Non-overlapping Intervals

non-overlapping-intervals/HC-kang.ts

@@ -0,0 +1,29 @@
+/**
+ * https://leetcode.com/problems/non-overlapping-intervals
+ * T.C. O(n logn)
+ * S.C. O(1)
+ * 
+ * [[1,2],[2,3],[3,4],[1,3]] =(sort by end)=> [[1,2],[2,3],[1,3],[3,4]]
+ * 
+ *    0 1 2 3 4...
+ *      [=)      pass
+ *        [=)    pass
+ *      [===)    count++
+ *      ^^^
+ *          [=)  pass
+ */
+function eraseOverlapIntervals(intervals: number[][]): number {
+  intervals.sort((a, b) => a[1] - b[1]);
+
+  let count = 0;
+  let end = -Infinity;
+
+  for (let i = 0; i < intervals.length; i++) {
+    if (intervals[i][0] < end) { // 
+      count++;
+    } else {
+      end = intervals[i][1];
+    }
+  }
+  return count;
+}