add merge intervals solution

Author: Tessa1217

merge-intervals/Tessa1217.java

@@ -0,0 +1,37 @@
+class Solution {
+    public int[][] merge(int[][] intervals) {
+
+        if (intervals.length <= 1) {
+            return intervals;
+        }
+
+        List<int[]> answer = new ArrayList<>();
+
+        Arrays.sort(intervals, (a, b) -> Integer.compare(a[0], b[0]));
+        
+        int start = intervals[0][0];
+        int end = intervals[0][1];
+
+        for (int i = 1; i < intervals.length; i++) {
+
+            // 현재 인터벌 시작점
+            int currStart = intervals[i][0];
+            // 현재 인터벌 끝점 
+            int currEnd = intervals[i][1];
+
+            if (end >= currStart) {
+                end = Math.max(end, currEnd);                
+            } else {
+                answer.add(new int[]{start, end});
+                start = currStart;      
+                end = currEnd;
+            }            
+        }
+
+        answer.add(new int[]{start, end});
+
+        return answer.stream()
+                            .toArray(int[][]::new);
+    }
+}
+