Commit #121 - Modified 4 file(s) - 13.06.2023 @23:18

Author: JRS296

Daily Questions/Equal Row and Column Pairs.java

@@ -0,0 +1,37 @@
+//Attempt #1 - 25mins
+//Link: https://leetcode.com/problems/equal-row-and-column-pairs/description/
+
+class Solution {
+    public int equalPairs(int[][] grid) {
+        int n = grid.length;
+        HashMap<String, Integer> hashMap = new HashMap<String, Integer>();
+        for(int [] row: grid){
+            String rowStr = Arrays.toString(row);
+            hashMap.put(rowStr, hashMap.getOrDefault(rowStr,0)+1);
+        }
+        
+        int count = 0;
+        for(int j = 0;j<n;j++){
+            int [] col = new int[n];
+            for(int i = 0;i<n;i++){
+                col[i] = grid[i][j];
+            }
+            count+=hashMap.getOrDefault(Arrays.toString(col),0);
+        }
+        return count;
+    }
+}
+
+/*
+Runtime
+49 ms
+Beats
+48.20%
+Memory
+46.1 MB
+Beats
+96.55%
+
+TC - O(n^2)
+SC - O(n^2)
+ */

Linked Lists/R - Reverse Linked List.java

@@ -91,4 +91,32 @@ public ListNode reverseList(ListNode head) {
 41.9 MB
 Beats
 74.65%
- */
+ */
+
+//Optimal Soln
+
+class Program {
+  public static LinkedList reverseLinkedList(LinkedList head) {
+    // Write your code here.
+    LinkedList current = head;
+    LinkedList prev = null;
+
+    while(current != null) {
+      LinkedList temp = current.next;
+      current.next = prev;
+      prev = current;
+      current = temp;
+    }
+    return prev;
+  }
+
+  static class LinkedList {
+    int value;
+    LinkedList next = null;
+
+    public LinkedList(int value) {
+      this.value = value;
+    }
+  }
+}
+

Linked Lists/Remove Nth Node From End of List.java

@@ -86,4 +86,41 @@ public ListNode removeNthFromEnd(ListNode head, int n) {
 Runtime: 1 ms
 Memory Usage: 42.5 MB
  */
-// Keypoint - Using extra space - for listnode x 
+// Keypoint - Using extra space - for listnode x 
+
+//Another Optimal:
+
+class Solution {
+    public ListNode removeNthFromEnd(ListNode head, int n) {
+       ListNode start = new ListNode();
+        start.next = head;
+        ListNode fast = start;
+        ListNode slow = start;     
+
+        for(int i = 1; i <= n; ++i)
+            fast = fast.next;
+    
+        while(fast.next != null)
+        {
+            fast = fast.next;
+            slow = slow.next;
+        }
+        
+        slow.next = slow.next.next;
+        
+        return start.next; 
+    }
+}
+
+/*
+Runtime
+0 ms
+Beats
+100%
+Memory
+40.8 MB
+Beats
+50.19%
+
+TC - O(n)
+ */