add a solution for 763

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_763.java

@@ -1,24 +1,26 @@
 package com.fishercoder.solutions;
 
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 public class _763 {
 
     public static class Solution1 {
-        public List<Integer> partitionLabels(String S) {
+        public List<Integer> partitionLabels(String s) {
             List<Integer> result = new ArrayList<>();
             int[] last = new int[26];
             /**This is the key step:
              * we find the last occurrence of each letter and record them in last[]*/
-            for (int i = 0; i < S.length(); i++) {
-                last[S.charAt(i) - 'a'] = i;
+            for (int i = 0; i < s.length(); i++) {
+                last[s.charAt(i) - 'a'] = i;
             }
             /**record the last end index of the current substring*/
             int end = 0;
             int start = 0;
-            for (int i = 0; i < S.length(); i++) {
-                end = Math.max(end, last[S.charAt(i) - 'a']);
+            for (int i = 0; i < s.length(); i++) {
+                end = Math.max(end, last[s.charAt(i) - 'a']);
                 if (end == i) {
                     result.add(end - start + 1);
                     start = end + 1;
@@ -28,4 +30,35 @@ public List partitionLabels(String S) {
         }
     }
 
+    public static class Solution2 {
+        /**
+         * My completely original solution on 10/14/2021.
+         *
+         * Again, using a pen and paper to visualize how this works,
+         * from the left to the right of the given string helps
+         * sort out the algorithm greatly and clears up any ambiguities!
+         */
+        public List<Integer> partitionLabels(String s) {
+            List<Integer> ans = new ArrayList<>();
+            Map<Character, Integer> lastIndexMap = new HashMap<>();
+            for (int i = 0; i < s.length(); i++) {
+                lastIndexMap.put(s.charAt(i), i);
+            }
+            for (int i = 0; i < s.length(); i++) {
+                int boundary = i;
+                int start = i;
+                do {
+                    int lastIndex = lastIndexMap.get(s.charAt(i));
+                    boundary = Math.max(lastIndex, boundary);
+                    i++;
+                } while (i < boundary);
+                if (i > boundary) {
+                    i--;
+                }
+                ans.add(boundary - start + 1);
+            }
+            return ans;
+        }
+    }
+
 }

src/test/java/com/fishercoder/_763Test.java

@@ -1,27 +1,50 @@
 package com.fishercoder;
 
 import com.fishercoder.solutions._763;
+
 import java.util.Arrays;
+import java.util.List;
+
 import org.junit.BeforeClass;
 import org.junit.Test;
 
 import static org.junit.Assert.assertEquals;
 
 public class _763Test {
-  private static _763.Solution1 solution1;
-
-  @BeforeClass
-  public static void setup() {
-    solution1 = new _763.Solution1();
-  }
-
-  @Test
-  public void test1() {
-    assertEquals(Arrays.asList(9, 7, 8), solution1.partitionLabels("ababcbacadefegdehijhklij"));
-  }
-
-  @Test
-  public void test2() {
-    assertEquals(Arrays.asList(9, 7, 8), solution1.partitionLabels("ababcbacadefegdehijhklij"));
-  }
+    private static _763.Solution1 solution1;
+    private static _763.Solution2 solution2;
+    private static List<Integer> expected;
+    private static String s;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _763.Solution1();
+        solution2 = new _763.Solution2();
+    }
+
+    @Test
+    public void test1() {
+        expected = Arrays.asList(9, 7, 8);
+        s = "ababcbacadefegdehijhklij";
+        assertEquals(expected, solution1.partitionLabels(s));
+        assertEquals(expected, solution2.partitionLabels(s));
+    }
+
+    @Test
+    public void test2() {
+        expected = Arrays.asList(10);
+        s = "eccbbbbdec";
+        assertEquals(expected, solution1.partitionLabels(s));
+        assertEquals(expected, solution2.partitionLabels(s));
+    }
+
+    @Test
+    public void test3() {
+        expected = Arrays.asList(1, 9);
+        s = "caedbdedda";
+        assertEquals(expected, solution1.partitionLabels(s));
+        assertEquals(expected, solution2.partitionLabels(s));
+    }
+
+
 }