Add Week 13 Solutions

insert-interval/bky373.java

@@ -0,0 +1,29 @@
+// time: O(N)
+// space: O(1)
+class Solution {
+
+    public int[][] insert(int[][] intervals, int[] newInterval) {
+        int n = intervals.length;
+        int i = 0;
+        List<int[]> result = new ArrayList<>();
+
+        while (i < n && intervals[i][1] < newInterval[0]) {
+            result.add(intervals[i]);
+            i++;
+        }
+
+        while (i < n && newInterval[1] >= intervals[i][0]) {
+            newInterval[0] = Math.min(newInterval[0], intervals[i][0]);
+            newInterval[1] = Math.max(newInterval[1], intervals[i][1]);
+            i++;
+        }
+        result.add(newInterval);
+
+        while (i < n) {
+            result.add(intervals[i]);
+            i++;
+        }
+
+        return result.toArray(new int[result.size()][]);
+    }
+}

meeting-rooms-ii/bky373.java

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+// time: O(n * log n)
+// space: O(n)
+class Solution {
+
+    public int minMeetingRooms(int[][] intervals) {
+        if (intervals.length == 0) {
+            return 0;
+        }
+
+        PriorityQueue<Integer> pq = new PriorityQueue<Integer>(
+                intervals.length,
+                new Comparator<Integer>() {
+                    public int compare(Integer a, Integer b) {
+                        return a - b;
+                    }
+                });
+
+        Arrays.sort(intervals, new Comparator<int[]>() {
+            public int compare(final int[] a, final int[] b) {
+                return a[0] - b[0];
+            }
+        });
+
+        pq.add(intervals[0][1]);
+
+        for (int i = 1; i < intervals.length; i++) {
+            if (intervals[i][0] >= pq.peek()) {
+                pq.poll();
+            }
+            pq.add(intervals[i][1]);
+        }
+
+        return pq.size();
+    }
+}

merge-intervals/bky373.java

@@ -0,0 +1,19 @@
+// time: O(n * log n)
+// space: O(log n)
+class Solution {
+
+    public int[][] merge(int[][] intervals) {
+        Arrays.sort(intervals, (a, b) -> Integer.compare(a[0], b[0]));
+        List<int[]> merged = new ArrayList<>();
+
+        for (int[] interval : intervals) {
+            if (merged.isEmpty() || merged.getLast()[1] < interval[0]) {
+                merged.add(interval);
+            } else {
+                merged.getLast()[1] = Math.max(merged.getLast()[1], interval[1]);
+            }
+        }
+
+        return merged.toArray(new int[merged.size()][]);
+    }
+}

non-overlapping-intervals/bky373.java

@@ -0,0 +1,22 @@
+// time: O(n * log n)
+// space: O(log n)
+class Solution {
+    public int eraseOverlapIntervals(int[][] intervals) {
+        Arrays.sort(intervals, Comparator.comparingInt(a -> a[1]));
+        int count = 0;
+        int min = Integer.MIN_VALUE;
+
+        for (int i=0; i<intervals.length; i++) {
+            int x = intervals[i][0];
+            int y = intervals[i][1];
+
+            if (x >= min) {
+                min = y;
+            } else {
+                count++;
+            }
+        }
+
+        return count;
+    }
+}

rotate-image/bky373.java

@@ -0,0 +1,17 @@
+// time: O(N), where N is the number of cells in the matrix
+// space: O(1)
+class Solution {
+
+    public void rotate(int[][] matrix) {
+        int n = matrix.length;
+        for (int i = 0; i < (n + 1) / 2; i++) {
+            for (int j = 0; j < n / 2; j++) {
+                int temp = matrix[n - 1 - j][i];
+                matrix[n - 1 - j][i] = matrix[n - 1 - i][n - j - 1];
+                matrix[n - 1 - i][n - j - 1] = matrix[j][n - 1 - i];
+                matrix[j][n - 1 - i] = matrix[i][j];
+                matrix[i][j] = temp;
+            }
+        }
+    }
+}