Java solution 264 && 295

Author: gavinfish

java/_264UglyNumberII.java

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+/**
+ * Write a program to find the n-th ugly number.
+ * Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 1, 2, 3, 4, 5, 6, 8, 9,
+ * 10, 12 is the sequence of the first 10 ugly numbers.
+ * <p>
+ * Note that 1 is typically treated as an ugly number, and n does not exceed 1690.
+ * <p>
+ * Credits:
+ * Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.
+ * <p>
+ * Created by drfish on 12/06/2017.
+ */
+public class _264UglyNumberII {
+    public int nthUglyNumber(int n) {
+        int index2 = 0, index3 = 0, index5 = 0;
+        int[] dp = new int[n];
+        dp[0] = 1;
+        for (int i = 1; i < n; i++) {
+            dp[i] = Math.min(dp[index2] * 2, Math.min(dp[index3] * 3, dp[index5] * 5));
+            if (dp[i] == dp[index2] * 2) {
+                index2++;
+            }
+            if (dp[i] == dp[index3] * 3) {
+                index3++;
+            }
+            if (dp[i] == dp[index5] * 5) {
+                index5++;
+            }
+        }
+        return dp[n - 1];
+    }
+
+    public static void main(String[] args) {
+        _264UglyNumberII solution = new _264UglyNumberII();
+        assert 1 == solution.nthUglyNumber(1);
+        assert 12 == solution.nthUglyNumber(10);
+    }
+}

java/_295FindMedianFromDataStream.java

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+import java.util.PriorityQueue;
+
+/**
+ * Median is the middle value in an ordered integer list. If the size of the list is even, there is no middle value.
+ * So the median is the mean of the two middle value.
+ * <p>
+ * Examples:
+ * [2,3,4] , the median is 3
+ * [2,3], the median is (2 + 3) / 2 = 2.5
+ * <p>
+ * Design a data structure that supports the following two operations:
+ * void addNum(int num) - Add a integer number from the data stream to the data structure.
+ * double findMedian() - Return the median of all elements so far.
+ * <p>
+ * For example:
+ * addNum(1)
+ * addNum(2)
+ * findMedian() -> 1.5
+ * addNum(3)
+ * findMedian() -> 2
+ * <p>
+ * Credits:
+ * Special thanks to @Louis1992 for adding this problem and creating all test cases.
+ * <p>
+ * Created by drfish on 13/06/2017.
+ */
+public class _295FindMedianFromDataStream {
+    public class MedianFinder {
+        private PriorityQueue<Integer> minHeap;
+        private PriorityQueue<Integer> maxHeap;
+        private boolean isEven = true;
+
+        /**
+         * initialize your data structure here.
+         */
+        public MedianFinder() {
+            minHeap = new PriorityQueue<>();
+            maxHeap = new PriorityQueue<>((n1, n2) -> n2 - n1);
+        }
+
+        public void addNum(int num) {
+            if (isEven) {
+                minHeap.offer(num);
+                maxHeap.offer(minHeap.poll());
+            } else {
+                maxHeap.offer(num);
+                minHeap.offer(maxHeap.poll());
+            }
+            isEven = !isEven;
+        }
+
+        public double findMedian() {
+            if (isEven) {
+                return (maxHeap.peek() + minHeap.peek()) / 2.0;
+            } else {
+                return maxHeap.peek();
+            }
+        }
+    }
+}