Add solution of ConsecutiveCharacters task

Author: andrei-punko

src/main/java/by/andd3dfx/string/ConsecutiveCharacters.java

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+package by.andd3dfx.string;
+
+/**
+ * <pre>
+ * <a href="https://leetcode.com/problems/consecutive-characters/">Task description</a>
+ *
+ * The power of the string is the maximum length of a non-empty substring that contains only one unique character.
+ *
+ * Given a string s, return the power of s.
+ *
+ * Example 1:
+ * Input: s = "leetcode"
+ * Output: 2
+ * Explanation: The substring "ee" is of length 2 with the character 'e' only.
+ *
+ * Example 2:
+ * Input: s = "abbcccddddeeeeedcba"
+ * Output: 5
+ * Explanation: The substring "eeeee" is of length 5 with the character 'e' only.
+ * </pre>
+ */
+public class ConsecutiveCharacters {
+
+    public static int maxPower(String s) {
+        var n = s.length();
+        var chars = s.toCharArray();
+
+        var left = 0;
+        var right = 0;
+        var max = 1;
+        var curr = 1;
+        while (right < n - 1) {
+            right++;
+            if (chars[right] == chars[left]) {
+                curr++;
+            } else {
+                left = right;
+                curr = 1;
+            }
+
+            if (curr > max) {
+                max = curr;
+            }
+        }
+
+        return max;
+    }
+}

src/test/java/by/andd3dfx/string/ConsecutiveCharactersTest.java

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+package by.andd3dfx.string;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.Test;
+
+public class ConsecutiveCharactersTest {
+
+    @Test
+    public void maxPower() {
+        assertThat(ConsecutiveCharacters.maxPower("abcdef")).isEqualTo(1);
+        assertThat(ConsecutiveCharacters.maxPower("ffffff")).isEqualTo(6);
+        assertThat(ConsecutiveCharacters.maxPower("ggwpbbbbaac")).isEqualTo(4);
+
+        assertThat(ConsecutiveCharacters.maxPower("leetcode")).isEqualTo(2);
+        assertThat(ConsecutiveCharacters.maxPower("abbcccddddeeeeedcba")).isEqualTo(5);
+    }
+}