Added 1 solution & refactored 2 solutions

varunu28 · varunu28 · commit 1965aab44257 · 2020-01-07T06:29:06.000-08:00
diff --git a/Easy/Decrypt String from Alphabet to Integer Mapping.java b/Easy/Decrypt String from Alphabet to Integer Mapping.java
@@ -0,0 +1,21 @@
+class Solution {
+  public String freqAlphabets(String s) {
+    StringBuilder sb = new StringBuilder();
+    int idx = 0;
+    int n = s.length();
+    while (idx < n) {
+      char c = s.charAt(idx);
+      int asciiAdd = -1;
+      if (idx + 2 < n && s.charAt(idx + 2) == '#') {
+        asciiAdd = Integer.parseInt(s.substring(idx, idx + 2));
+        idx += 3;
+      }
+      else {
+        asciiAdd = Integer.parseInt(s.substring(idx, idx + 1));
+        idx++;
+      }
+      sb.append((char) (96 + asciiAdd));
+    }
+    return sb.toString();
+  }
+}
diff --git a/Easy/Repeated Substring Pattern.java b/Easy/Repeated Substring Pattern.java
@@ -1,8 +1,19 @@
 class Solution {
-    public boolean repeatedSubstringPattern(String s) {
-        String s1 = s + s;
-        String s2 = s1.substring(1,s1.length()-1);
-        
-        return s2.contains(s);
+  public boolean repeatedSubstringPattern(String s) {
+    int n = s.length();
+    for (int i = n / 2; i >= 0; i--) {
+      if (i != 0 && n % i == 0) {
+        int count = n / i;
+        StringBuilder sb = new StringBuilder();
+        String sub = s.substring(0, i);
+        while (count-- > 0) {
+          sb.append(sub);
+        }
+        if (sb.toString().equals(s)) {
+          return true;
+        }
+      }
     }
+    return false;
+  }
 }
diff --git a/Medium/Find Peak Element.java b/Medium/Find Peak Element.java
@@ -1,39 +1,25 @@
 class Solution {
-    public static int findPeakElement(int[] nums) {
-        if (nums.length == 1) {
-            return 0;
-        }
-        
-        return findPeakElementImpl(nums, 0, nums.length-1);
-    }
-
-    private static int findPeakElementImpl(int[] nums, int start, int end) {
-        if (start > end) {
-            return -1;
-        }
-
-        int mid = (start + end)/2;
-
-        if (mid == 0 && nums.length > 1) {
-            if (nums[mid] > nums[mid+1]) {
-                return mid;
-            }
-        }
-        else if (mid == nums.length-1 && nums.length > 1) {
-            if (nums[mid] > nums[mid-1]) {
-                return mid;
-            }
-        }
-        else {
-            if (nums.length > 1) {
-                if (nums[mid] > nums[mid-1] && nums[mid] > nums[mid+1]) {
-                    return mid;
-                }
-            }
-        }
-
-        int left = findPeakElementImpl(nums, start, mid-1);
-
-        return left == -1 ? findPeakElementImpl(nums, mid+1, end) : left;
+  public int findPeakElement(int[] nums) {
+    int[] index = {-1};
+    helper(nums, 0, nums.length - 1, index);
+    return index[0];
+  }
+  
+  private void helper(int[] nums, int start, int end, int[] index) {
+    if (start <= end && index[0] == -1) {
+      int mid = (start + end) / 2;
+      boolean found = (
+          (mid + 1 < nums.length ? nums[mid] > nums[mid + 1] : true) &&
+          (mid - 1 >= 0 ? nums[mid] > nums[mid - 1] : true)
+        );
+      if (found) {
+        index[0] = mid;
+        return;
+      }
+      else {
+        helper(nums, start, mid - 1, index);
+        helper(nums, mid + 1, end, index);
+      }
     }
+  }
 }
