diff --git a/src/main/java/g0301_0400/s0374_guess_number_higher_or_lower/Solution.java b/src/main/java/g0301_0400/s0374_guess_number_higher_or_lower/Solution.java
new file mode 100644
index 000000000..a682e6399
--- /dev/null
+++ b/src/main/java/g0301_0400/s0374_guess_number_higher_or_lower/Solution.java
@@ -0,0 +1,34 @@
+package g0301_0400.s0374_guess_number_higher_or_lower;
+
+// #Easy #Binary_Search #Interactive
+
+/**
+ * Forward declaration of guess API.
+ *
+ * @param num your guess
+ * @return -1 if num is lower than the guess number 1 if num is higher than the guess number
+ * otherwise return 0 int guess(int num);
+ */
+public class Solution {
+ public int guessNumber(int n) {
+ int left = 1;
+ int right = n;
+ int mid;
+ while (left <= right) { + mid = left + (right - left) / 2; + if (guess(mid) == 1) { + left = mid + 1; + } else if (guess(mid) == -1) { + right = mid - 1; + } else { + return mid; + } + } + return -1; + } + + // Assume we pick 7 + private int guess(int num) { + return Integer.compare(7, num); + } +} diff --git a/src/main/java/g0301_0400/s0374_guess_number_higher_or_lower/readme.md b/src/main/java/g0301_0400/s0374_guess_number_higher_or_lower/readme.md new file mode 100644 index 000000000..17b675e9d --- /dev/null +++ b/src/main/java/g0301_0400/s0374_guess_number_higher_or_lower/readme.md @@ -0,0 +1,46 @@ +374\. Guess Number Higher or Lower + +Easy + +We are playing the Guess Game. The game is as follows: + +I pick a number from `1` to `n`. You have to guess which number I picked. + +Every time you guess wrong, I will tell you whether the number I picked is higher or lower than your guess. + +You call a pre-defined API `int guess(int num)`, which returns 3 possible results: + +* `-1`: The number I picked is lower than your guess (i.e. `pick < num`). +* `1`: The number I picked is higher than your guess (i.e. `pick> num`).
+* `0`: The number I picked is equal to your guess (i.e. `pick == num`).
+
+Return _the number that I picked_.
+
+**Example 1:**
+
+**Input:** n = 10, pick = 6
+
+**Output:** 6
+
+**Example 2:**
+
+**Input:** n = 1, pick = 1
+
+**Output:** 1
+
+**Example 3:**
+
+**Input:** n = 2, pick = 1
+
+**Output:** 1
+
+**Example 4:**
+
+**Input:** n = 2, pick = 2
+
+**Output:** 2
+
+**Constraints:**
+
+* <code>1 <= n <= 2<sup>31</sup> - 1</code>
+* `1 <= pick <= n` \ No newline at end of file diff --git a/src/main/java/g0301_0400/s0378_kth_smallest_element_in_a_sorted_matrix/Solution.java b/src/main/java/g0301_0400/s0378_kth_smallest_element_in_a_sorted_matrix/Solution.java new file mode 100644 index 000000000..431861b35 --- /dev/null +++ b/src/main/java/g0301_0400/s0378_kth_smallest_element_in_a_sorted_matrix/Solution.java @@ -0,0 +1,52 @@ +package g0301_0400.s0378_kth_smallest_element_in_a_sorted_matrix; + +// #Medium #Top_Interview_Questions #Array #Sorting #Binary_Search #Matrix #Heap_Priority_Queue + +public class Solution { + public int kthSmallest(int[][] matrix, int k) { + if (matrix == null &#124;&#124; matrix.length == 0) { + return -1; + } + int start = matrix[0][0]; + int end = matrix[matrix.length - 1][matrix[0].length - 1]; + // O(log(max-min)) time + while (start + 1 < end) { + int mid = start + (end - start) / 2; + if (countLessEqual(matrix, mid) < k) { + // look towards end + start = mid; + } else { + // look towards start + end = mid; + } + } + + // leave only with start and end, one of them must be the answer + // try to see if start fits the criteria first + if (countLessEqual(matrix, start)>= k) {
+ return start;
+ } else {
+ return end;
+ }
+ }
+
+ // countLessEqual
+ // O(n) Time
+ private int countLessEqual(int[][] matrix, int target) {
+ // binary elimination from top right
+ int row = 0;
+ int col = matrix[0].length - 1;
+ int count = 0;
+ while (row < matrix.length && col>= 0) {
+ if (matrix[row][col] <= target) { + // get the count in current row + count += col + 1; + row++; + } else if (matrix[row][col]> target) {
+ // eliminate the current col
+ col--;
+ }
+ }
+ return count;
+ }
+}
diff --git a/src/main/java/g0301_0400/s0378_kth_smallest_element_in_a_sorted_matrix/readme.md b/src/main/java/g0301_0400/s0378_kth_smallest_element_in_a_sorted_matrix/readme.md
new file mode 100644
index 000000000..85803a3c0
--- /dev/null
+++ b/src/main/java/g0301_0400/s0378_kth_smallest_element_in_a_sorted_matrix/readme.md
@@ -0,0 +1,36 @@
+378\. Kth Smallest Element in a Sorted Matrix
+
+Medium
+
+Given an `n x n` `matrix` where each of the rows and columns is sorted in ascending order, return _the_ <code>k<sup>th</sup></code> _smallest element in the matrix_.
+
+Note that it is the <code>k<sup>th</sup></code> smallest element **in the sorted order**, not the <code>k<sup>th</sup></code> **distinct** element.
+
+You must find a solution with a memory complexity better than <code>O(n<sup>2</sup>)</code>.
+
+**Example 1:**
+
+**Input:** matrix = \[\[1,5,9\],\[10,11,13\],\[12,13,15\]\], k = 8
+
+**Output:** 13
+
+**Explanation:** The elements in the matrix are \[1,5,9,10,11,12,13,**13**,15\], and the 8<sup>th</sup> smallest number is 13
+
+**Example 2:**
+
+**Input:** matrix = \[\[-5\]\], k = 1
+
+**Output:** -5
+
+**Constraints:**
+
+* `n == matrix.length == matrix[i].length`
+* `1 <= n <= 300` +* <code>-10<sup>9</sup> <= matrix[i][j] <= 10<sup>9</sup></code>
+* All the rows and columns of `matrix` are **guaranteed** to be sorted in **non-decreasing order**.
+* <code>1 <= k <= n<sup>2</sup></code>
+
+**Follow up:**
+
+* Could you solve the problem with a constant memory (i.e., `O(1)` memory complexity)?
+* Could you solve the problem in `O(n)` time complexity? The solution may be too advanced for an interview but you may find reading [this paper](http://www.cse.yorku.ca/~andy/pubs/X+Y.pdf) fun.
\ No newline at end of file
diff --git a/src/main/java/g0301_0400/s0380_insert_delete_getrandom_o1/RandomizedSet.java b/src/main/java/g0301_0400/s0380_insert_delete_getrandom_o1/RandomizedSet.java
new file mode 100644
index 000000000..a979a2c6d
--- /dev/null
+++ b/src/main/java/g0301_0400/s0380_insert_delete_getrandom_o1/RandomizedSet.java
@@ -0,0 +1,64 @@
+package g0301_0400.s0380_insert_delete_getrandom_o1;
+
+// #Medium #Top_Interview_Questions #Array #Hash_Table #Math #Design #Randomized
+
+import java.security.SecureRandom;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class RandomizedSet {
+ private final SecureRandom rand;
+ private final List<integer> list;
+ private final Map<integer, Integer> map;
+
+ // Initialize your data structure here.
+ public RandomizedSet() {
+ this.rand = new SecureRandom();
+ this.list = new ArrayList<strong>();
+ this.map = new HashMap<strong>();
+ }
+
+ // Inserts a value to the set. Returns true if the set did not already contain the specified
+ // element.
+
+ public boolean insert(int val) {
+ if (this.map.containsKey(val)) {
+ return false;
+ }
+ this.list.add(val);
+ this.map.put(val, list.size() - 1);
+ return true;
+ }
+
+ // Removes a value from the set. Returns true if the set contained the specified element.
+ public boolean remove(int val) {
+ if (!this.map.containsKey(val)) {
+ return false;
+ }
+ int index = this.map.get(val);
+ if (index == this.list.size() - 1) {
+ this.list.remove(index);
+ this.map.remove(val);
+ return true;
+ }
+ int value = list.get(list.size() - 1);
+ this.list.set(index, value);
+ this.list.remove(this.list.size() - 1);
+ this.map.remove(val);
+ this.map.put(value, index);
+ return true;
+ }
+
+ // Get a random element from the set.
+ public int getRandom() {
+ return this.list.get(rand.nextInt(list.size()));
+ }
+}
+
+/*
+ * Your RandomizedSet object will be instantiated and called as such: RandomizedSet obj = new
+ * RandomizedSet(); boolean param_1 = obj.insert(val); boolean param_2 = obj.remove(val); int
+ * param_3 = obj.getRandom();
+ */
diff --git a/src/main/java/g0301_0400/s0380_insert_delete_getrandom_o1/readme.md b/src/main/java/g0301_0400/s0380_insert_delete_getrandom_o1/readme.md
new file mode 100644
index 000000000..d1e0c081c
--- /dev/null
+++ b/src/main/java/g0301_0400/s0380_insert_delete_getrandom_o1/readme.md
@@ -0,0 +1,38 @@
+380\. Insert Delete GetRandom O(1)
+
+Medium
+
+Implement the `RandomizedSet` class:
+
+* `RandomizedSet()` Initializes the `RandomizedSet` object.
+* `bool insert(int val)` Inserts an item `val` into the set if not present. Returns `true` if the item was not present, `false` otherwise.
+* `bool remove(int val)` Removes an item `val` from the set if present. Returns `true` if the item was present, `false` otherwise.
+* `int getRandom()` Returns a random element from the current set of elements (it's guaranteed that at least one element exists when this method is called). Each element must have the **same probability** of being returned.
+
+You must implement the functions of the class such that each function works in **average** `O(1)` time complexity.
+
+**Example 1:**
+
+**Input** 
+
+ \["RandomizedSet", "insert", "remove", "insert", "getRandom", "remove", "insert", "getRandom"\] 
+ \[\[\], \[1\], \[2\], \[2\], \[\], \[1\], \[2\], \[\]\]
+
+**Output:** \[null, true, false, true, 2, true, false, 2\]
+
+**Explanation:** 
+
+ RandomizedSet randomizedSet = new RandomizedSet(); 
+ randomizedSet.insert(1); // Inserts 1 to the set. Returns true as 1 was inserted successfully. 
+ randomizedSet.remove(2); // Returns false as 2 does not exist in the set. 
+ randomizedSet.insert(2); // Inserts 2 to the set, returns true. Set now contains \[1,2\]. 
+ randomizedSet.getRandom(); // getRandom() should return either 1 or 2 randomly. 
+ randomizedSet.remove(1); // Removes 1 from the set, returns true. Set now contains \[2\]. 
+ randomizedSet.insert(2); // 2 was already in the set, so return false. 
+ randomizedSet.getRandom(); // Since 2 is the only number in the set, getRandom() will always return 2.
+
+**Constraints:**
+
+* <code>-2<sup>31</sup> <= val <= 2<sup>31</sup> - 1</code>
+* At most `2 * `<code>10<sup>5</sup></code> calls will be made to `insert`, `remove`, and `getRandom`.
+* There will be **at least one** element in the data structure when `getRandom` is called.
\ No newline at end of file
diff --git a/src/test/java/g0301_0400/s0374_guess_number_higher_or_lower/SolutionTest.java b/src/test/java/g0301_0400/s0374_guess_number_higher_or_lower/SolutionTest.java
new file mode 100644
index 000000000..51fc1bcff
--- /dev/null
+++ b/src/test/java/g0301_0400/s0374_guess_number_higher_or_lower/SolutionTest.java
@@ -0,0 +1,28 @@
+package g0301_0400.s0374_guess_number_higher_or_lower;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class SolutionTest {
+ @Test
+ void guessNumber() {
+ assertThat(new Solution().guessNumber(10), equalTo(7));
+ }
+
+ @Test
+ void guessNumber2() {
+ assertThat(new Solution().guessNumber(1), equalTo(-1));
+ }
+
+ @Test
+ void guessNumber3() {
+ assertThat(new Solution().guessNumber(2), equalTo(-1));
+ }
+
+ @Test
+ void guessNumber4() {
+ assertThat(new Solution().guessNumber(6), equalTo(-1));
+ }
+}
diff --git a/src/test/java/g0301_0400/s0378_kth_smallest_element_in_a_sorted_matrix/SolutionTest.java b/src/test/java/g0301_0400/s0378_kth_smallest_element_in_a_sorted_matrix/SolutionTest.java
new file mode 100644
index 000000000..c7e4a948b
--- /dev/null
+++ b/src/test/java/g0301_0400/s0378_kth_smallest_element_in_a_sorted_matrix/SolutionTest.java
@@ -0,0 +1,20 @@
+package g0301_0400.s0378_kth_smallest_element_in_a_sorted_matrix;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class SolutionTest {
+ @Test
+ void kthSmallest() {
+ assertThat(
+ new Solution().kthSmallest(new int[][] {{1, 5, 9}, {10, 11, 13}, {12, 13, 15}}, 8),
+ equalTo(13));
+ }
+
+ @Test
+ void kthSmallest2() {
+ assertThat(new Solution().kthSmallest(new int[][] {{-5}}, 1), equalTo(-5));
+ }
+}
diff --git a/src/test/java/g0301_0400/s0380_insert_delete_getrandom_o1/RandomizedSetTest.java b/src/test/java/g0301_0400/s0380_insert_delete_getrandom_o1/RandomizedSetTest.java
new file mode 100644
index 000000000..b47c9d07c
--- /dev/null
+++ b/src/test/java/g0301_0400/s0380_insert_delete_getrandom_o1/RandomizedSetTest.java
@@ -0,0 +1,38 @@
+package g0301_0400.s0380_insert_delete_getrandom_o1;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+
+class RandomizedSetTest {
+ @Test
+ void randomizedSet() {
+ List<string> result = new ArrayList<strong>();
+ RandomizedSet randomizedSet = null;
+ result.add(randomizedSet + "");
+ randomizedSet = new RandomizedSet();
+ result.add(randomizedSet.insert(1) + "");
+ result.add(randomizedSet.remove(2) + "");
+ result.add(randomizedSet.insert(2) + "");
+ int random = randomizedSet.getRandom();
+ result.add(random + "");
+ result.add(randomizedSet.remove(1) + "");
+ result.add(randomizedSet.insert(2) + "");
+ result.add(randomizedSet.getRandom() + "");
+ List<string> expected =
+ new ArrayList<strong>(
+ Arrays.asList("null", "true", "false", "true", "1", "true", "false", "2"));
+ List<string> expected2 =
+ new ArrayList<strong>(
+ Arrays.asList("null", "true", "false", "true", "2", "true", "false", "2"));
+ if (random == 1) {
+ assertThat(result, equalTo(expected));
+ } else {
+ assertThat(result, equalTo(expected2));
+ }
+ }
+}
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