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System Design Tools and Templates
Posted in system design
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Interview Resources
Pramp
BigOCheatSheet
Hackerrank
Grokking the system design interview
Cracking the coding interview
Leetcode
Posted in resources
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common git problems
Delete the remote branch
git push -d origin <branch_name>
Delete the local branch
git branch -D <branch_name>
Merge master into feature branch
git checkout master
git pull
git checkout feature
git merge master
Checkout from a specific commit
Use git checkout <sha1> to check out a particular commit
git checkout -b <branch> <commit>
Revert commit
git revert <commit_hash>
git revert <oldest_commit_hash>..<latest_commit_hash>
Setting your branch to exactly match the remote branch can be done in two steps:
git fetch origin
git reset –hard origin/master
Remove a file from PR
git checkout origin/master — src/main/java/HelloWorld.java
git commit -m “Removed files from PR”
Sync your fork with original
# Add a new remote upstream repository
git remote add upstream https://github.com/ORIGINAL_OWNER/ORIGINAL_REPOSITORY.git
# Sync your fork
git fetch upstream
git checkout master
git merge upstream/master
git remote add upstream <>
If you need to remove a single file from the staging area, use
git reset HEAD — <file>
Remove submodule dirty
git submodule foreach –recursive git checkout .
git submodule update –force –recursive –init –remote
Posted in git
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longest-substring-without-duplicate-characters
public class LengthOfLongestSubstring {
public static int lengthOfLongestSubstring(String s) {
if (s == null) {
return 0;
}
Map<Character, Integer> map = new HashMap<>();
int maxLength = 0;
int start = 0;
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
Integer duplicateIndex = map.put(c, i);
if (duplicateIndex != null) {
if (duplicateIndex >= start) {
maxLength = Math.max(maxLength, i - start);
start = duplicateIndex + 1;
}
}
}
return Math.max(maxLength, s.length() - start);
}
public static void main(String[] args) {
int maxLength = lengthOfLongestSubstring("abcabcbb"); // 3
System.out.println(maxLength);
maxLength = lengthOfLongestSubstring("bbbbb"); // 1
System.out.println(maxLength);
maxLength = lengthOfLongestSubstring("b"); // 1
System.out.println(maxLength);
maxLength = lengthOfLongestSubstring(""); // 0
System.out.println(maxLength);
maxLength = lengthOfLongestSubstring(null); // 0
System.out.println(maxLength);
}
}
Posted in hashtable
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sorted-square
public class SortedSquare {
public static int[] sortedSquare(int[] nums) {
int[] result = new int[nums.length];
int writeIndex = nums.length - 1;
int l = 0, r = nums.length - 1;
while (l <= r) {
if (nums[l] * nums[l] < nums[r] * nums[r]) {
result[writeIndex] = nums[r] * nums[r];
r--;
} else {
result[writeIndex] = nums[l] * nums[l];
l++;
}
writeIndex--;
}
return result;
}
public static void main(String[] args) {
Utils.printArray(sortedSquare(new int[]{-4, -2, -1, 0, 1, 3, 5}));
}
}
Posted in sorting
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sum-of-left-leaves
package us.inest.app.dcp.recursion;
import us.inest.app.dcp.tree.TreeNode;
public class SumOfLeftLeaves {
public static int sumOfLeftLeaves(TreeNode root) {
// base case
if (root == null) {
return 0;
}
// left child is a leaf node
if (root.left != null && root.left.left == null && root.left.right == null) {
return root.left.data + sumOfLeftLeaves(root.right);
}
return sumOfLeftLeaves(root.left) + sumOfLeftLeaves(root.right);
}
}
Posted in recursion
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remove-nth-node-from-end-of-list
LeetCode link: https://leetcode.com/problems/remove-nth-node-from-end-of-list/submissions/684704570/
Java Solution
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* 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) {
ListNode first = head;
//null list
if (head == null) {
return head;
}
for (int i = 0; i < n; i++) {
if (first.next == null) {
return (i == n - 1) ? head.next : head;
}
first = first.next;
}
ListNode second = head;
while (first.next != null) {
first = first.next;
second = second.next;
}
second.next = second.next.next;
return head;
}
}
Posted in singly-linked list
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