add 1180

fishercoder1534 · fishercoder1534 · commit 9d1c67048a02 · 2020-02-01T07:42:25.000-08:00
diff --git a/README.md b/README.md
@@ -46,6 +46,7 @@ _If you like this project, please leave me a star._ &#9733;
 |1189|[Maximum Number of Balloons](https://leetcode.com/problems/maximum-number-of-balloons/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1189.java) |[:tv:](https://youtu.be/LGgMZC0vj5s) |Easy||
 |1185|[Day of the Week](https://leetcode.com/problems/day-of-the-week/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1185.java) | |Easy||
 |1184|[Distance Between Bus Stops](https://leetcode.com/problems/distance-between-bus-stops/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1184.java) | [:tv:](https://www.youtube.com/watch?v=RFq7yA5iyhI)|Easy||
+|1180|[Count Substrings with Only One Distinct Letter](https://leetcode.com/problems/count-substrings-with-only-one-distinct-letter/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1180.java) | |Easy|Math, String|
 |1165|[Single-Row Keyboard](https://leetcode.com/problems/single-row-keyboard/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1165.java) | |Easy||
 |1160|[Find Words That Can Be Formed by Characters](https://leetcode.com/problems/find-words-that-can-be-formed-by-characters/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1160.java)| |Easy||
 |1154|[Day of the Year](https://leetcode.com/problems/day-of-the-year/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1154.java) | |Easy||
diff --git a/src/main/java/com/fishercoder/solutions/_1180.java b/src/main/java/com/fishercoder/solutions/_1180.java
@@ -0,0 +1,49 @@
+package com.fishercoder.solutions;
+
+/**
+ * 1180. Count Substrings with Only One Distinct Letter
+ *
+ * Given a string S, return the number of substrings that have only one distinct letter.
+ *
+ * Example 1:
+ * Input: S = "aaaba"
+ * Output: 8
+ * Explanation: The substrings with one distinct letter are "aaa", "aa", "a", "b".
+ * "aaa" occurs 1 time.
+ * "aa" occurs 2 times.
+ * "a" occurs 4 times.
+ * "b" occurs 1 time.
+ * So the answer is 1 + 2 + 4 + 1 = 8.
+ *
+ * Example 2:
+ * Input: S = "aaaaaaaaaa"
+ * Output: 55
+ *
+ * Constraints:
+ * 1 <= S.length <= 1000
+ * S[i] consists of only lowercase English letters.
+ * */
+public class _1180 {
+    public static class Solution1 {
+        public int countLetters(String S) {
+            int count = 0;
+            for (int i = 0, j = 1; j < S.length() && i <= j; ) {
+                while (j < S.length() && S.charAt(i) == S.charAt(j)) {
+                    j++;
+                }
+                count += countTimes(S.substring(i, j));
+                i += S.substring(i, j).length();
+            }
+            return count;
+        }
+
+        private int countTimes(String str) {
+            int len = str.length();
+            int times = 0;
+            while (len > 0) {
+                times += len--;
+            }
+            return times;
+        }
+    }
+}
diff --git a/src/test/java/com/fishercoder/_1180Test.java b/src/test/java/com/fishercoder/_1180Test.java
@@ -0,0 +1,26 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._1180;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class _1180Test {
+    private static _1180.Solution1 solution1;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _1180.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        assertEquals(8, solution1.countLetters("aaaba"));
+    }
+
+    @Test
+    public void test2() {
+        assertEquals(55, solution1.countLetters("aaaaaaaaaa"));
+    }
+}
