fishercoder1534 · xdongyan · Aug 8, 2017 · Aug 8, 2017 · Aug 8, 2017 · Aug 8, 2017
diff --git a/.idea/compiler.xml b/.idea/compiler.xml
diff --git a/.idea/libraries/Maven__junit_junit_4_12.xml b/.idea/libraries/Maven__junit_junit_4_12.xml
diff --git a/.idea/libraries/Maven__org_hamcrest_hamcrest_core_1_3.xml b/.idea/libraries/Maven__org_hamcrest_hamcrest_core_1_3.xml
diff --git a/.idea/misc.xml b/.idea/misc.xml
diff --git a/.idea/modules.xml b/.idea/modules.xml
diff --git a/.idea/vcs.xml b/.idea/vcs.xml
diff --git a/leetcode-algorithms.iml b/leetcode-algorithms.iml
@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module org.jetbrains.idea.maven.project.MavenProjectsManager.isMavenModule="true" type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" LANGUAGE_LEVEL="JDK_1_8">
+    <output url="file://$MODULE_DIR$/target/classes" />
+    <output-test url="file://$MODULE_DIR$/target/test-classes" />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/src/main/java" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/src/test/java" isTestSource="true" />
+      <excludeFolder url="file://$MODULE_DIR$/target" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+    <orderEntry type="library" scope="TEST" name="Maven: junit:junit:4.12" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: org.hamcrest:hamcrest-core:1.3" level="project" />
+  </component>
+</module>
diff --git a/src/main/java/com/fishercoder/solutions/_451.java b/src/main/java/com/fishercoder/solutions/_451.java
@@ -44,9 +44,11 @@
  */
 public class _451 {
 
-    public String frequencySort(String s) {
+    public static String frequencySort(String s) {
         Map<Character, Integer> map = new HashMap();
-        for (char c : s.toCharArray()) map.put(c, map.getOrDefault(c, 0) + 1);
+        for (char c : s.toCharArray()) {
+            map.put(c, map.getOrDefault(c, 0) + 1);
+        }
         List<Map.Entry<Character, Integer>> list = new ArrayList<>(map.entrySet());
         Collections.sort(list, (o1, o2) -> (o2.getValue()).compareTo(o1.getValue()));
         StringBuilder stringBuilder = new StringBuilder();
@@ -57,4 +59,8 @@ public String frequencySort(String s) {
         }
         return stringBuilder.toString();
     }
+    public static void main(String[] args) {
+        String s = "trete" ;
+        System.out.println(frequencySort(s));
+    }
 }
diff --git a/src/main/java/com/fishercoder/solutions/_459.java b/src/main/java/com/fishercoder/solutions/_459.java
@@ -27,17 +27,36 @@ public static boolean repeatedSubstringPattern(String str) {
         pattern[0] = 0;
 
         while (j < n) {
-            if (str.charAt(cur) == str.charAt(j)){
+            if (str.charAt(cur) == str.charAt(j)) {
                 pattern[j++] = ++cur;
             } else {
                 if (cur == 0) pattern[j++] = 0;
                 else cur = pattern[cur-1];//start from beginning of current matching pattern.
             }
         }
 
-        return (pattern[n-1] > 0 && n%(n-pattern[n-1]) == 0);
+        return (pattern[n - 1] > 0 && n % (n-pattern[n - 1]) == 0);
+    }
+    // the idea is that the length substring will be divisor of the length s, then find the
+    //sub string and append s.length/sub.length times to check if the string is equaled to the original string.
+    //credit:
+    public static boolean repeatedSubstringPattern_2(String s) {
+        int len = s.length();
+        for (int i = len/2; i >=1; i--) {
+            if (len % i == 0) {
+                int n = len / i;
+                String sub = s.substring(0, i);
+                StringBuilder sb = new StringBuilder();
+                for (int j = 0; j < n; j++) {
+                    sb.append(sub);
+                }
+                if (sb.toString().equals(s)) {
+                    return true;
+                }
+            }
+        }
+        return false;
     }
-
     public static void main(String...args){
 //        String str = "aba";
 //        String str = "abab";//should be true
@@ -47,5 +66,6 @@ public static void main(String...args){
 //        String str = "abababc";
         String str = "abababaaba";
         System.out.println(repeatedSubstringPattern(str));
+        System.out.println(repeatedSubstringPattern_2(str));
     }
 }