merge-intervals

Author: chjung99

merge-intervals/chjung99.java

@@ -0,0 +1,49 @@
+class Solution {
+    public int[][] merge(int[][] intervals) {
+        //sort by start_i
+        List<Interval> ordered = new ArrayList<>();
+        for (int i = 0; i < intervals.length; i++){
+            ordered.add(new Interval(intervals[i]));
+        }
+        Collections.sort(ordered);
+
+        Deque<Interval> queue = new ArrayDeque<>();
+        queue.add(ordered.get(0));
+        //merge in order
+        for (int i = 1; i < ordered.size(); i++) {
+            Interval tail = queue.removeLast();
+            Interval cur = ordered.get(i);
+
+            if (tail.end >= cur.start){
+                Interval merged = new Interval(new int[]{Math.min(tail.start, cur.start), Math.max(tail.end, cur.end)});
+                queue.add(merged);
+            } else{
+                queue.add(tail);
+                queue.add(cur);
+            }
+        }
+        int[][] answer = new int[queue.size()][2];
+        int idx = 0;
+        while (!queue.isEmpty()){
+            answer[idx++] = queue.removeFirst().raw;
+        }
+        return answer;
+    }
+    class Interval implements Comparable<Interval>{
+        int[] raw;
+        int start;
+        int end;
+
+        public Interval(int[] raw){
+            this.raw = raw;
+            this.start = raw[0];
+            this.end = raw[1];
+        }
+        @Override
+        public int compareTo(Interval o){
+            return Integer.compare(this.start, o.start);
+        }
+    }
+}
+
+