add a solution for 76

fishercoder1534 · fishercoder1534 · commit cff80141f4ae · 2021-10-20T15:57:29.000-07:00
diff --git a/src/main/java/com/fishercoder/solutions/_76.java b/src/main/java/com/fishercoder/solutions/_76.java
@@ -41,4 +41,45 @@ public String minWindow(String s, String t) {
             return s.substring(minStart, minStart + minLen);
         }
     }
+
+    public static class Solution2 {
+        /**
+         * I implemented below solution on my own following the hints on LeetCode.
+         * In comparison, Solution1 is more optimized and runs faster.
+         */
+        public String minWindow(String s, String t) {
+            if (t.length() > s.length()) {
+                return "";
+            }
+            int[] tCount = new int[256];
+            for (int i = 0; i < t.length(); i++) {
+                tCount[t.charAt(i)]++;
+            }
+            int left = 0;
+            int right = 0;
+            int[] sCount = new int[256];
+            String ans = "";
+            while (right < s.length()) {
+                sCount[s.charAt(right)]++;
+                while (isValid(sCount, tCount)) {
+                    if (right - left < ans.length() || ans.equals("")) {
+                        ans = s.substring(left, right + 1);
+                    }
+                    sCount[s.charAt(left)]--;
+                    left++;
+                }
+                right++;
+            }
+            return ans;
+        }
+
+        private boolean isValid(int[] sCount, int[] tCount) {
+            for (int i = 0; i < sCount.length; i++) {
+                if (sCount[i] < tCount[i]) {
+                    return false;
+                }
+            }
+            return true;
+        }
+    }
 }
diff --git a/src/test/java/com/fishercoder/_76Test.java b/src/test/java/com/fishercoder/_76Test.java
@@ -7,16 +7,42 @@
 import static org.junit.Assert.assertEquals;
 
 public class _76Test {
-  private static _76.Solution1 solution1;
-  private static int[] nums;
+    private static _76.Solution1 solution1;
+    private static _76.Solution2 solution2;
+    private static String expected;
+    private static String s;
+    private static String t;
 
-  @BeforeClass
-  public static void setup() {
-    solution1 = new _76.Solution1();
-  }
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _76.Solution1();
+        solution2 = new _76.Solution2();
+    }
 
-  @Test
-  public void test1() {
-    assertEquals("BANC", solution1.minWindow("ADOBECODEBANC", "ABC"));
-  }
+    @Test
+    public void test1() {
+        expected = "BANC";
+        s = "ADOBECODEBANC";
+        t = "ABC";
+        assertEquals(expected, solution1.minWindow(s, t));
+        assertEquals(expected, solution2.minWindow(s, t));
+    }
+
+    @Test
+    public void test2() {
+        expected = "";
+        s = "A";
+        t = "B";
+        assertEquals(expected, solution1.minWindow(s, t));
+        assertEquals(expected, solution2.minWindow(s, t));
+    }
+
+    @Test
+    public void test3() {
+        expected = "cwae";
+        s = "cabwefgewcwaefgcf";
+        t = "cae";
+        assertEquals(expected, solution1.minWindow(s, t));
+        assertEquals(expected, solution2.minWindow(s, t));
+    }
 }
