844. Backspace String Compare (#39)

* 844. Backspace String Compare * Add missing link
xtenzQ · Jul 30, 2024 · ca83de2 · ca83de2
1 parent fba0fc1
commit ca83de2
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diff --git a/algorithms-and-data-structures/src/main/java/com/xtenzq/stack/Stacks.java b/algorithms-and-data-structures/src/main/java/com/xtenzq/stack/Stacks.java
@@ -56,4 +56,33 @@ public static String removeDuplicates(String s) {
         }
         return sb.toString();
     }
+
+    /**
+     * Given two strings {@code s} and {@code t}, return {@code true} if they are equal when both are typed
+     * into empty text editors. {@code #} means a backspace character.
+     *
+     * @param s first string
+     * @param t second string
+     * @return {@code true} if strings are equal, {@code false} otherwise
+     * @implNote This method runs in {@code O(n + m} time and space complexity, where {@code n} and {@code m} are
+     * the lengths of strings {@code s} and {@code t}
+     * @see <a href="https://leetcode.com/problems/backspace-string-compare/">844. Backspace String Compare</a>
+     */
+    public static boolean backspaceCompare(String s, String t) {
+        Stack<Character> sStack = clearStack(s);
+        Stack<Character> tStack = clearStack(t);
+        return tStack.equals(sStack);
+    }
+
+    private static Stack<Character> clearStack(String s) {
+        Stack<Character> stack = new Stack<>();
+        for (int i = 0; i < s.length(); i++) {
+            if (s.charAt(i) != '#') {
+                stack.push(s.charAt(i));
+            } else if (!stack.empty()) {
+                stack.pop();
+            }
+        }
+        return stack;
+    }
 }
diff --git a/algorithms-and-data-structures/src/test/java/com/xtenzq/stack/StacksTest.java b/algorithms-and-data-structures/src/test/java/com/xtenzq/stack/StacksTest.java
@@ -2,6 +2,7 @@
 
 import org.junit.jupiter.api.Test;
 
+import static com.xtenzq.stack.Stacks.backspaceCompare;
 import static com.xtenzq.stack.Stacks.isValid;
 import static com.xtenzq.stack.Stacks.removeDuplicates;
 import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -34,4 +35,19 @@ void removeDuplicates_test1() {
     void removeDuplicates_test2() {
         assertEquals("ay", removeDuplicates("azxxzy"));
     }
+
+    @Test
+    void backspaceCompare_case1() {
+        assertTrue(backspaceCompare("ab#c", "ad#c"));
+    }
+
+    @Test
+    void backspaceCompare_case2() {
+        assertTrue(backspaceCompare("ab##", "c#d#"));
+    }
+
+    @Test
+    void backspaceCompare_case3() {
+        assertFalse(backspaceCompare("a#c", "b"));
+    }
 }