solve 56.merge-intervals

Author: andavid

vscode/56.merge-intervals.java

@@ -0,0 +1,63 @@
+/*
+ * @lc app=leetcode id=56 lang=java
+ *
+ * [56] Merge Intervals
+ *
+ * https://leetcode.com/problems/merge-intervals/description/
+ *
+ * algorithms
+ * Medium (35.46%)
+ * Likes:    2345
+ * Dislikes: 183
+ * Total Accepted:    380.4K
+ * Total Submissions: 1.1M
+ * Testcase Example:  '[[1,3],[2,6],[8,10],[15,18]]'
+ *
+ * Given a collection of intervals, merge all overlapping intervals.
+ *
+ * Example 1:
+ *
+ *
+ * Input: [[1,3],[2,6],[8,10],[15,18]]
+ * Output: [[1,6],[8,10],[15,18]]
+ * Explanation: Since intervals [1,3] and [2,6] overlaps, merge them into
+ * [1,6].
+ *
+ *
+ * Example 2:
+ *
+ *
+ * Input: [[1,4],[4,5]]
+ * Output: [[1,5]]
+ * Explanation: Intervals [1,4] and [4,5] are considered overlapping.
+ *
+ * NOTE: input types have been changed on April 15, 2019. Please reset to
+ * default code definition to get new method signature.
+ *
+ */
+class Solution {
+  public int[][] merge(int[][] intervals) {
+    if (intervals.length <= 1) {
+      return intervals;
+    }
+
+    Arrays.sort(intervals, (i1, i2) -> Integer.compare(i1[0], i2[0]));
+
+    List<int[]> result = new ArrayList<>();
+    int[] last = intervals[0];
+    result.add(last);
+
+    for (int i = 1; i < intervals.length; i++) {
+      int[] interval = intervals[i];
+      if (last[1] < interval[0]) {
+        result.add(interval);
+        last = interval;
+      } else if (last[1] < interval[1]) {
+        last[1] = interval[1];
+      }
+    }
+
+    return result.toArray(new int[result.size()][]);
+  }
+}
+