solves positions of large groups

Author: anishLearnsToCode

README.md

@@ -1,7 +1,7 @@
 # LeetCode Algorithms
 
-![problems-solved](https://img.shields.io/badge/Problems%20Solved-192/2081-1f425f.svg)
-![problems-solved-java](https://img.shields.io/badge/Java-192/2081-1abc9c.svg)
+![problems-solved](https://img.shields.io/badge/Problems%20Solved-193/2081-1f425f.svg)
+![problems-solved-java](https://img.shields.io/badge/Java-193/2081-1abc9c.svg)
 ![problems-solved-python](https://img.shields.io/badge/Python-186/2081-1abc9c.svg)
 [![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg)](CONTRIBUTING.md)
 [![cp](https://img.shields.io/badge/also%20see-Competitve%20Programming-1f72ff.svg)](https://github.com/anishLearnsToCode/competitive-programming)
@@ -223,7 +223,7 @@
 | 819 | [Most Common Word](https://leetcode.com/problems/most-common-word) | [![Java](assets/java.png)](src/MostCommonWord.java) |
 | 821 | [Shortest Distance to Character](https://leetcode.com/problems/shortest-distance-to-a-character) | [![Java](assets/java.png)](src/ShortestDistanceToACharacter.java) |
 | 824 | [Goat Latin](https://leetcode.com/problems/goat-latin) | [![Java](assets/java.png)](src/GoatLatin.java) |
-| 830 | [Positions of Large Groups](https://leetcode.com/problems/positions-of-large-groups) | |
+| 830 | [Positions of Large Groups](https://leetcode.com/problems/positions-of-large-groups) | [![Java](assets/java.png)](src/PositionsOfLargeGroups.java) |
 | 832 | [Flipping an Image](https://leetcode.com/problems/flipping-an-image) | |
 | 836 | [Rectangle Overlap](https://leetcode.com/problems/rectangle-overlap) | |
 | 840 | [Magic Squares in Grid](https://leetcode.com/problems/magic-squares-in-grid) | |

src/PositionsOfLargeGroups.java

@@ -0,0 +1,19 @@
+import java.util.ArrayList;
+import java.util.List;
+
+public class PositionsOfLargeGroups {
+    public List<List<Integer>> largeGroupPositions(String s) {
+        List<List<Integer>> result = new ArrayList<>();
+        char current = s.charAt(0);
+        int start = 0;
+        for (int index = 1 ; index < s.length() ; index++) {
+            if (s.charAt(index) != current) {
+                if (index - start >= 3) result.add(List.of(start, index - 1));
+                start = index;
+                current = s.charAt(index);
+            }
+        }
+        if (s.length() - start >= 3) result.add(List.of(start, s.length() - 1));
+        return result;
+    }
+}