diff --git a/src/main/java/com/thealgorithms/strings/ReverseString.java b/src/main/java/com/thealgorithms/strings/ReverseString.java index 54a9b779e828..996aa68bb307 100644 --- a/src/main/java/com/thealgorithms/strings/ReverseString.java +++ b/src/main/java/com/thealgorithms/strings/ReverseString.java @@ -1,5 +1,7 @@ package com.thealgorithms.strings; +import java.util.Stack; + /** * Reverse String using different version */ @@ -57,4 +59,31 @@ public static String reverse3(String string) { } return sb.toString(); } + /** + * Reverses the given string using a stack. + * This method uses a stack to reverse the characters of the string. + * * @param str The input string to be reversed. + * @return The reversed string. + */ + public static String reverseStringUsingStack(String str) { + // Check if the input string is null + if (str == null) { + throw new IllegalArgumentException("Input string cannot be null"); + } + Stack stack = new Stack<>(); + StringBuilder reversedString = new StringBuilder(); + // Check if the input string is empty + if (str.isEmpty()) { + return str; + } + // Push each character of the string onto the stack + for (char ch : str.toCharArray()) { + stack.push(ch); + } + // Pop each character from the stack and append to the StringBuilder + while (!stack.isEmpty()) { + reversedString.append(stack.pop()); + } + return reversedString.toString(); + } } diff --git a/src/test/java/com/thealgorithms/strings/ReverseStringTest.java b/src/test/java/com/thealgorithms/strings/ReverseStringTest.java index 08f5fb586d82..476765b00dfc 100644 --- a/src/test/java/com/thealgorithms/strings/ReverseStringTest.java +++ b/src/test/java/com/thealgorithms/strings/ReverseStringTest.java @@ -1,8 +1,10 @@ package com.thealgorithms.strings; import static org.junit.jupiter.api.Assertions.assertEquals; +import static org.junit.jupiter.api.Assertions.assertThrows; import java.util.stream.Stream; +import org.junit.jupiter.api.Test; import org.junit.jupiter.params.ParameterizedTest; import org.junit.jupiter.params.provider.Arguments; import org.junit.jupiter.params.provider.MethodSource; @@ -31,4 +33,15 @@ public void testReverseString2(String input, String expectedOutput) { public void testReverseString3(String input, String expectedOutput) { assertEquals(expectedOutput, ReverseString.reverse3(input)); } + + @ParameterizedTest + @MethodSource("testCases") + public void testReverseStringUsingStack(String input, String expectedOutput) { + assertEquals(expectedOutput, ReverseString.reverseStringUsingStack(input)); + } + + @Test + public void testReverseStringUsingStackWithNullInput() { + assertThrows(IllegalArgumentException.class, () -> ReverseString.reverseStringUsingStack(null)); + } } pFad - Phonifier reborn

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