add 1375

fishercoder1534 · fishercoder1534 · commit f8f4288b1431 · 2020-03-08T07:53:45.000-07:00
diff --git a/README.md b/README.md
@@ -8,6 +8,7 @@ _If you like this project, please leave me a star._ &#9733;
 
 |  #  |      Title     |   Solutions   | Video  | Difficulty  | Tag                   
 |-----|----------------|---------------|--------|-------------|-------------
+|1375|[ Bulb Switcher III](https://leetcode.com/problems/bulb-switcher-iii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1375.java) | |Medium||Array
 |1374|[Generate a String With Characters That Have Odd Counts](https://leetcode.com/problems/generate-a-string-with-characters-that-have-odd-counts/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1374.java) | |Easy||String
 |1373|[Maximum Sum BST in Binary Tree](https://leetcode.com/problems/maximum-sum-bst-in-binary-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1373.java) | |Hard||DP, BST
 |1372|[Longest ZigZag Path in a Binary Tree](https://leetcode.com/problems/longest-zigzag-path-in-a-binary-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1372.java) | |Hard||DP, Tree
diff --git a/src/main/java/com/fishercoder/solutions/_1375.java b/src/main/java/com/fishercoder/solutions/_1375.java
@@ -0,0 +1,62 @@
+package com.fishercoder.solutions;
+
+/**
+ * 1375. Bulb Switcher III
+ *
+ * There is a room with n bulbs, numbered from 1 to n, arranged in a row from left to right. Initially, all the bulbs are turned off.
+ * At moment k (for k from 0 to n - 1), we turn on the light[k] bulb. A bulb change color to blue only if it is on and all the previous bulbs (to the left) are turned on too.
+ * Return the number of moments in which all turned on bulbs are blue.
+ *
+ * Example 1:
+ * Input: light = [2,1,3,5,4]
+ * Output: 3
+ * Explanation: All bulbs turned on, are blue at the moment 1, 2 and 4.
+ *
+ * Example 2:
+ * Input: light = [3,2,4,1,5]
+ * Output: 2
+ * Explanation: All bulbs turned on, are blue at the moment 3, and 4 (index-0).
+ *
+ * Example 3:
+ * Input: light = [4,1,2,3]
+ * Output: 1
+ * Explanation: All bulbs turned on, are blue at the moment 3 (index-0).
+ * Bulb 4th changes to blue at the moment 3.
+ *
+ * Example 4:
+ * Input: light = [2,1,4,3,6,5]
+ * Output: 3
+ *
+ * Example 5:
+ * Input: light = [1,2,3,4,5,6]
+ * Output: 6
+ *
+ * Constraints:
+ * n == light.length
+ * 1 <= n <= 5 * 10^4
+ * light is a permutation of  [1, 2, ..., n]
+ * */
+public class _1375 {
+    public static class Solution1 {
+        public int numTimesAllBlue(int[] light) {
+            int blues = 0;
+            int[] status = new int[light.length];//0 means off, 1 means on
+            for (int i = 0; i < light.length; i++) {
+                status[light[i] - 1] = 1;
+                if (checkAllBlues(status, i)) {
+                    blues++;
+                }
+            }
+            return blues;
+        }
+
+        private boolean checkAllBlues(int[] status, int endIndex) {
+            for (int i = 0; i <= endIndex; i++) {
+                if (status[i] != 1) {
+                    return false;
+                }
+            }
+            return true;
+        }
+    }
+}
diff --git a/src/test/java/com/fishercoder/_1375Test.java b/src/test/java/com/fishercoder/_1375Test.java
@@ -0,0 +1,36 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._1375;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class _1375Test {
+    private static _1375.Solution1 solution1;
+    private static int[] light;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _1375.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        light = new int[]{2, 1, 3, 5, 4};
+        assertEquals(3, solution1.numTimesAllBlue(light));
+    }
+
+    @Test
+    public void test2() {
+        light = new int[]{3, 2, 4, 1, 5};
+        assertEquals(2, solution1.numTimesAllBlue(light));
+    }
+
+    @Test
+    public void test3() {
+        light = new int[]{1, 2, 3, 4, 5, 6};
+        assertEquals(6, solution1.numTimesAllBlue(light));
+    }
+
+}
