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Commit fd5926f

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[Function add]
1. Add leetcode solutions with tag Amazon.
1 parent 5fc32ef commit fd5926f

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‎leetcode/289. Game of Life.md

Lines changed: 36 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -124,4 +124,39 @@ class Solution {
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return count;
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}
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}
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```
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```
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### Amazon Session
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* Method 1: Bit Manipulation
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1. Use the second lowest bit to save the state of next generation.
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2. State compression: use a 3 * 3 matrix to traversal the board
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* if count == 3: current is live and 2 neighbors, current is dead and 3 neighbors(reproduction).
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* count - board = 3, current is live and 3 neighbors, so count is 4.
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```Java
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class Solution {
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public void gameOfLife(int[][] board) {
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if(board == null || board.length == 0 || board[0].length == 0) return;
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int height = board.length, width = board[0].length;
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for(int i = 0; i < height; i++){
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for(int j = 0; j < width; j++){
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//center is (i, j)
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int count = 0;
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for(int p = Math.max(0, i - 1); p <= Math.min(height - 1, i + 1); p++){
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for(int q = Math.max(0, j - 1); q <= Math.min(width - 1, j + 1); q++){
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count += board[p][q] & 1;
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}
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}
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if(count == 3 || count - board[i][j] == 3) board[i][j] |= 0B10;
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}
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}
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for(int i = 0; i < height; i++){
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for(int j = 0; j < width; j++){
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board[i][j] >>= 1;
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}
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}
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}
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}
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```
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### Reference
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1. [花花酱 LeetCode 289. Game of Life](http://zxi.mytechroad.com/blog/simulation/leetcode-289-game-of-life/);

‎leetcode/445. Add Two Numbers II.md

Lines changed: 124 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -171,5 +171,129 @@ Output: 7 -> 8 -> 0 -> 7
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}
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```
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### Amazon Session
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* Method 1: recursion
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```Java
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/**
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* Definition for singly-linked list.
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* public class ListNode {
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* int val;
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* ListNode next;
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* ListNode(int x) { val = x; }
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* }
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*/
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class Solution {
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private int len1;
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private int len2;
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public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
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ListNode cur1 = l1;
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int len1 = 0;
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while(cur1 != null){
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len1++;
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cur1 = cur1.next;
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}
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ListNode cur2 = l2;
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int len2 = 0;
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while(cur2 != null){
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len2++;
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cur2 = cur2.next;
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}
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this.len1 = Math.max(len1, len2);
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this.len2 = Math.min(len1, len2);
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ListNode first = len1 >= len2 ? l1: l2;
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ListNode second = len1 >= len2 ? l2: l1;
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ListNode next = add(first, this.len1 - 1, second, this.len2 - 1);
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if(next.val < 10) return next;
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else{
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int carry = next.val / 10;
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next.val %= 10;
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ListNode res = new ListNode(carry);
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res.next = next;
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return res;
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}
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}
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public ListNode add(ListNode l1, int index1, ListNode l2, int index2){ // we garantee l1 is longer
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if(index1 == 0 && index2 == 0){
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return new ListNode(l1.val + l2.val);
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}else if(index1 > index2){
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ListNode next = add(l1.next, index1 - 1, l2, index2);
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int carry = next.val / 10;
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next.val %= 10;
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ListNode res = new ListNode(carry + l1.val);
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res.next = next;
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return res;
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}else{
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ListNode next = add(l1.next, index1 - 1, l2.next, index2 - 1);
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int carry = next.val / 10;
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next.val %= 10;
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ListNode res = new ListNode(carry + l1.val + l2.val);
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res.next = next;
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return res;
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}
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}
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}
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```
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* Method 2: reverse the string
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```Java
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/**
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* Definition for singly-linked list.
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* public class ListNode {
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* int val;
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* ListNode next;
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* ListNode(int x) { val = x; }
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* }
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*/
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class Solution {
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public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
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ListNode cur1 = l1, pre1 = null;
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while(cur1 != null){
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ListNode next = cur1.next;
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cur1.next = pre1;
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pre1 = cur1;
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cur1 = next;
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}
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ListNode cur2 = l2, pre2 = null;
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while(cur2 != null){
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ListNode next = cur2.next;
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cur2.next = pre2;
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pre2 = cur2;
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cur2 = next;
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}
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ListNode dummy = new ListNode(1), cur = dummy;
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// pre1 && pre2 are the new heads
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int carry = 0;
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while(pre1 != null || pre2 != null){
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int sum = 0;
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if(pre1 != null && pre2 != null){
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sum = pre1.val + pre2.val + carry;
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pre1 = pre1.next;
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pre2 = pre2.next;
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}else if(pre1 != null){
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sum = pre1.val + carry;
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pre1 = pre1.next;
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}else{
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sum = pre2.val + carry;
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pre2 = pre2.next;
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}
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carry = sum / 10;
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cur.next = new ListNode(sum % 10);
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cur = cur.next;
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}
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if(carry != 0) cur.next = new ListNode(1);
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ListNode res = dummy.next;
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cur2 = res; pre2 = null;
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while(cur2 != null){
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ListNode next = cur2.next;
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cur2.next = pre2;
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pre2 = cur2;
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cur2 = next;
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}
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return pre2;
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}
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}
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```
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### Reference
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1. [Java O(n) recursive solution by counting the difference of length](https://leetcode.com/problems/add-two-numbers-ii/discuss/92643/Java-O(n)-recursive-solution-by-counting-the-difference-of-length)

‎leetcode/588. Design In-Memory File System.md

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Original file line numberDiff line numberDiff line change
@@ -113,3 +113,82 @@ Note:
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* String param_4 = obj.readContentFromFile(filePath);
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*/
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```
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### Amazon Session
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* Method 1: Tire Tree
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```Java
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class FileSystem {
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private static final class Node{
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boolean isFile;
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String path;
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String content;
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Map<String, Node> map; //key is path name, value is child nodes.
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public Node(String path){
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this.map = new TreeMap<>();
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this.path = path;
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}
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}
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private Node root;
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public FileSystem() {
133+
this.root = new Node("/");
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root.path = "/";
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this.root.isFile = false;
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}
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private List<String> getListFromNode(Node node){
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List<String> res = new ArrayList<>();
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if(node.isFile){
140+
res.add(node.path);
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return res;
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}
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res.addAll(node.map.keySet());
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res.sort((a, b)->{
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return a.compareTo(b);
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});
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return res;
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}
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public List<String> ls(String path) {
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String[] tokens = path.split("\\/");
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List<String> result = new ArrayList<>();
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if(path.equals("/")) return getListFromNode(root);
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Node temp = this.root;
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for(int i = 1; i < tokens.length; i++){
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if(!temp.map.containsKey(tokens[i])) return result;
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temp = temp.map.get(tokens[i]);
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}
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return getListFromNode(temp);
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}
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private Node createOrGetByPath(String path){
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String[] tokens = path.split("\\/");
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Node temp = this.root;
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for(int i = 1; i < tokens.length; i++){
164+
if(!temp.map.containsKey(tokens[i])) temp.map.put(tokens[i], new Node(tokens[i]));
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temp = temp.map.get(tokens[i]);
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}
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return temp;
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}
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public void mkdir(String path) {
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createOrGetByPath(path);
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}
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public void addContentToFile(String filePath, String content) {
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Node file = createOrGetByPath(filePath);
174+
if(file.content == null){
175+
file.isFile = true;
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file.content = content;
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}else{
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file.content += content;
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}
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}
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public String readContentFromFile(String filePath) {
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Node file = createOrGetByPath(filePath);
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return file.content;
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}
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}
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/**
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* Your FileSystem object will be instantiated and called as such:
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* FileSystem obj = new FileSystem();
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* List<String> param_1 = obj.ls(path);
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* obj.mkdir(path);
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* obj.addContentToFile(filePath,content);
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* String param_4 = obj.readContentFromFile(filePath);
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*/
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```

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