Modified 3 solutions

varunu28 · varunu28 · commit bafda67bb5a6 · 2020-08-31T20:34:12.000-05:00
diff --git a/Easy/Jewels and Stones.java b/Easy/Jewels and Stones.java
@@ -1,19 +1,15 @@
 class Solution {
   public int numJewelsInStones(String J, String S) {
-    Map<Character, Integer> mapJ = getMap(J);
-    Map<Character, Integer> mapS = getMap(S);
+    Set<Character> set = new HashSet<>();
+    for (char c : J.toCharArray()) {
+      set.add(c);
+    }
     int count = 0;
-    for (Character key : mapJ.keySet()) {
-      count += mapS.getOrDefault(key, 0);
+    for (char c : S.toCharArray()) {
+      if (set.contains(c)) {
+        count++;
+      }
     }
     return count;
   }
-  
-  private Map<Character, Integer> getMap(String s) {
-    Map<Character, Integer> map = new HashMap<>();
-    for (char c : s.toCharArray()) {
-      map.put(c, map.getOrDefault(c, 0) + 1);
-    }
-    return map;
-  }
 }
diff --git a/Medium/Remove Nth Node From End of List.java b/Medium/Remove Nth Node From End of List.java
@@ -3,36 +3,31 @@
  * public class ListNode {
  *     int val;
  *     ListNode next;
- *     ListNode(int x) { val = x; }
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
  * }
  */
 class Solution {
-    public ListNode removeNthFromEnd(ListNode head, int n) {
-        
-        if (head ==  null || head.next == null) return null;
-        
-        ListNode curr = head;
-        int i = 0;
-        
-        while (curr != null) {
-            curr = curr.next;
-            i++;
-        }
-        
-        if (i == n) {
-            return head.next;
-        }
-        
-        n = i - n;
-        i = 1;
-        curr = head;
-        
-        while (i != n) {
-            curr = curr.next;
-            i++;
-        }
-        curr.next = curr.next.next;
-        
-        return head;
+  public ListNode removeNthFromEnd(ListNode head, int n) {
+    if (head == null || n == 0) {
+      return head;
     }
+    ListNode slow = head;
+    int count = 0;
+    while (count < n) {
+      slow = slow.next;
+      count++;
+    }
+    if (slow == null) {
+      return head.next;
+    }
+    ListNode fast = head;
+    while (slow.next != null) {
+      slow = slow.next;
+      fast = fast.next;
+    }
+    fast.next = fast.next.next;
+    return head;
+  }
 }
diff --git a/Medium/Subsets.java b/Medium/Subsets.java
@@ -1,24 +1,19 @@
 class Solution {
   public List<List<Integer>> subsets(int[] nums) {
     List<List<Integer>> list = new ArrayList<>();
-    List<Integer> curr = new ArrayList<>();
-    helper(list, curr, nums, 0, nums.length, new boolean[nums.length]);
+    helper(nums, list, new ArrayList<>(), 0);
     return list;
-  }   
+  }
   
-  private void helper(List<List<Integer>> list, List<Integer> curr, int[] nums, int idx, int n, boolean[] seen) {
+  private void helper(int[] nums, List<List<Integer>> list, List<Integer> curr, int idx) {
     list.add(new ArrayList<>(curr));
-    if (idx >= n) {
+    if (idx >= nums.length) {
       return;
     }
-    for (int i = idx; i < n; i++) {
-      if (!seen[i]) {
-        seen[i] = true;
-        curr.add(nums[i]);
-        helper(list, curr, nums, i + 1, n, seen);
-        seen[i] = false;
-        curr.remove(curr.size() - 1);
-      }
+    for (int i = idx; i < nums.length; i++) {
+      curr.add(nums[i]);
+      helper(nums, list, curr, i + 1);
+      curr.remove(curr.size() - 1);
     }
   }
 }
