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ThanhNITThanhNIT
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Updated tasks 49-79
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‎README.md

Lines changed: 22 additions & 22 deletions
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‎src/main/java/g0001_0100/s0049_group_anagrams/Solution.java

Lines changed: 14 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -2,24 +2,28 @@
22

33
// #Medium #Top_100_Liked_Questions #Top_Interview_Questions #Array #String #Hash_Table #Sorting
44
// #Data_Structure_II_Day_8_String #Programming_Skills_II_Day_11 #Udemy_Strings
5-
// #Big_O_Time_O(n*k_log_k)_Space_O(n) #2023_08_11_Time_6_ms_(92.28%)_Space_46.4_MB_(98.50%)
5+
// #Big_O_Time_O(n*k_log_k)_Space_O(n) #2024_11_11_Time_6_ms_(97.61%)_Space_47.7_MB_(69.56%)
66

77
import java.util.ArrayList;
8-
import java.util.Arrays;
98
import java.util.HashMap;
109
import java.util.List;
1110
import java.util.Map;
1211

12+
@SuppressWarnings("java:S3824")
1313
public class Solution {
1414
public List<List<String>> groupAnagrams(String[] strs) {
15-
Map<String, List<String>> hm = new HashMap<>();
16-
for (String s : strs) {
17-
char[] ch = s.toCharArray();
18-
Arrays.sort(ch);
19-
String temp = new String(ch);
20-
hm.computeIfAbsent(temp, k -> new ArrayList<>());
21-
hm.get(temp).add(s);
15+
Map<String, List<String>> anagrams = new HashMap<>();
16+
for (String word : strs) {
17+
char[] freq = new char[26];
18+
for (char c : word.toCharArray()) {
19+
freq[c - 'a']++;
20+
}
21+
String keyString = new String(freq);
22+
if (!anagrams.containsKey(keyString)) {
23+
anagrams.put(keyString, new ArrayList<>());
24+
}
25+
anagrams.get(keyString).add(word);
2226
}
23-
return (new ArrayList<>(hm.values()));
27+
return new ArrayList<>(anagrams.values());
2428
}
2529
}

‎src/main/java/g0001_0100/s0051_n_queens/Solution.java

Lines changed: 42 additions & 30 deletions
Original file line numberDiff line numberDiff line change
@@ -1,50 +1,62 @@
11
package g0001_0100.s0051_n_queens;
22

33
// #Hard #Top_100_Liked_Questions #Array #Backtracking #Big_O_Time_O(N!)_Space_O(N)
4-
// #2023_08_11_Time_1_ms_(100.00%)_Space_43.6_MB_(97.17%)
4+
// #2024_11_11_Time_1_ms_(99.77%)_Space_44.8_MB_(61.16%)
55

66
import java.util.ArrayList;
7-
import java.util.Arrays;
7+
import java.util.LinkedList;
88
import java.util.List;
99

1010
public class Solution {
1111
public List<List<String>> solveNQueens(int n) {
12-
boolean[] pos = new boolean[n + 2 * n - 1 + 2 * n - 1];
13-
int[] pos2 = new int[n];
14-
List<List<String>> ans = new ArrayList<>();
15-
helper(n, 0, pos, pos2, ans);
16-
return ans;
12+
char[][] board = new char[n][n];
13+
for (int i = 0; i < n; i++) {
14+
for (int j = 0; j < n; j++) {
15+
board[i][j] = '.';
16+
}
17+
}
18+
List<List<String>> res = new ArrayList<>();
19+
int[] leftRow = new int[n];
20+
int[] upperDiagonal = new int[2 * n - 1];
21+
int[] lowerDiagonal = new int[2 * n - 1];
22+
solve(0, board, res, leftRow, lowerDiagonal, upperDiagonal);
23+
return res;
1724
}
1825

19-
private void helper(int n, int row, boolean[] pos, int[] pos2, List<List<String>> ans) {
20-
if (row == n) {
21-
construct(n, pos2, ans);
26+
void solve(
27+
int col,
28+
char[][] board,
29+
List<List<String>> res,
30+
int[] leftRow,
31+
int[] lowerDiagonal,
32+
int[] upperDiagonal) {
33+
if (col == board.length) {
34+
res.add(construct(board));
2235
return;
2336
}
24-
for (int i = 0; i < n; i++) {
25-
int index = n + 2 * n - 1 + n - 1 + i - row;
26-
if (pos[i] || pos[n + i + row] || pos[index]) {
27-
continue;
37+
for (int row = 0; row < board.length; row++) {
38+
if (leftRow[row] == 0
39+
&& lowerDiagonal[row + col] == 0
40+
&& upperDiagonal[board.length - 1 + col - row] == 0) {
41+
board[row][col] = 'Q';
42+
leftRow[row] = 1;
43+
lowerDiagonal[row + col] = 1;
44+
upperDiagonal[board.length - 1 + col - row] = 1;
45+
solve(col + 1, board, res, leftRow, lowerDiagonal, upperDiagonal);
46+
board[row][col] = '.';
47+
leftRow[row] = 0;
48+
lowerDiagonal[row + col] = 0;
49+
upperDiagonal[board.length - 1 + col - row] = 0;
2850
}
29-
pos[i] = true;
30-
pos[n + i + row] = true;
31-
pos[index] = true;
32-
pos2[row] = i;
33-
helper(n, row + 1, pos, pos2, ans);
34-
pos[i] = false;
35-
pos[n + i + row] = false;
36-
pos[index] = false;
3751
}
3852
}
3953

40-
private void construct(int n, int[] pos, List<List<String>> ans) {
41-
List<String> sol = new ArrayList<>();
42-
for (int r = 0; r < n; r++) {
43-
char[] queenRow = new char[n];
44-
Arrays.fill(queenRow, '.');
45-
queenRow[pos[r]] = 'Q';
46-
sol.add(new String(queenRow));
54+
List<String> construct(char[][] board) {
55+
List<String> res = new LinkedList<>();
56+
for (char[] chars : board) {
57+
String s = new String(chars);
58+
res.add(s);
4759
}
48-
ans.add(sol);
60+
return res;
4961
}
5062
}

‎src/main/java/g0001_0100/s0053_maximum_subarray/Solution.java

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
// #Medium #Top_100_Liked_Questions #Top_Interview_Questions #Array #Dynamic_Programming
44
// #Divide_and_Conquer #Data_Structure_I_Day_1_Array #Dynamic_Programming_I_Day_5
55
// #Udemy_Famous_Algorithm #Big_O_Time_O(n)_Space_O(1)
6-
// #2023_08_11_Time_1_ms_(100.00%)_Space_57.7_MB_(90.58%)
6+
// #2024_11_11_Time_1_ms_(99.32%)_Space_56.9_MB_(54.82%)
77

88
public class Solution {
99
public int maxSubArray(int[] nums) {

‎src/main/java/g0001_0100/s0055_jump_game/Solution.java

Lines changed: 12 additions & 31 deletions
Original file line numberDiff line numberDiff line change
@@ -2,41 +2,22 @@
22

33
// #Medium #Top_100_Liked_Questions #Top_Interview_Questions #Array #Dynamic_Programming #Greedy
44
// #Algorithm_II_Day_12_Dynamic_Programming #Dynamic_Programming_I_Day_4 #Udemy_Arrays
5-
// #Big_O_Time_O(n)_Space_O(1) #2023_08_11_Time_2_ms_(79.47%)_Space_44.8_MB_(22.14%)
5+
// #Big_O_Time_O(n)_Space_O(1) #2024_11_11_Time_1_ms_(100.00%)_Space_45.6_MB_(44.48%)
66

77
public class Solution {
88
public boolean canJump(int[] nums) {
9-
int sz = nums.length;
10-
// we set 1 so it won't break on the first iteration
11-
int tmp = 1;
12-
for (int i = 0; i < sz; i++) {
13-
// we always deduct tmp for every iteration
14-
tmp--;
15-
if (tmp < 0) {
16-
// if from previous iteration tmp is already 0, it will be <0 here
17-
// leading to false value
18-
return false;
19-
}
20-
// we get the maximum value because this value is supposed
21-
// to be our iterator, if both values are 0, then the next
22-
// iteration we will return false
23-
// if either both or one of them are not 0 then we will keep doing this and check.
24-
25-
// We can stop the whole iteration with this condition. without this condition the code
26-
// runs in 2ms 79.6%, adding this condition improves the performance into 1ms 100%
27-
// because if the test case jump value is quite large, instead of just iterate, we can
28-
// just check using this condition
29-
// example: [10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] -> we can just jump to the end without
30-
// iterating whole array
31-
tmp = Math.max(tmp, nums[i]);
32-
if (i + tmp >= sz - 1) {
33-
return true;
9+
if (nums.length == 1) {
10+
return true;
11+
}
12+
if (nums[0] == 0) {
13+
return false;
14+
}
15+
int fin = nums.length - 1;
16+
for (int i = nums.length - 2; i >= 0; i--) {
17+
if ((nums[i] + i) >= fin) {
18+
fin = i;
3419
}
3520
}
36-
// we can just return true at the end, because if tmp is 0 on previous
37-
// iteration,
38-
// even though the next iteration index is the last one, it will return false under the
39-
// tmp<0 condition
40-
return true;
21+
return fin == 0;
4122
}
4223
}

‎src/main/java/g0001_0100/s0056_merge_intervals/Solution.java

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@
22

33
// #Medium #Top_100_Liked_Questions #Top_Interview_Questions #Array #Sorting
44
// #Data_Structure_II_Day_2_Array #Level_2_Day_17_Interval #Udemy_2D_Arrays/Matrix
5-
// #Big_O_Time_O(n_log_n)_Space_O(n) #2023_08_11_Time_8_ms_(96.27%)_Space_45.2_MB_(90.13%)
5+
// #Big_O_Time_O(n_log_n)_Space_O(n) #2024_11_11_Time_7_ms_(98.37%)_Space_46.8_MB_(11.43%)
66

77
import java.util.ArrayList;
88
import java.util.Arrays;

‎src/main/java/g0001_0100/s0062_unique_paths/Solution.java

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
// #Medium #Top_100_Liked_Questions #Top_Interview_Questions #Dynamic_Programming #Math
44
// #Combinatorics #Algorithm_II_Day_13_Dynamic_Programming #Dynamic_Programming_I_Day_15
55
// #Level_1_Day_11_Dynamic_Programming #Big_O_Time_O(m*n)_Space_O(m*n)
6-
// #2023_08_11_Time_0_ms_(100.00%)_Space_39.2_MB_(67.74%)
6+
// #2024_11_11_Time_0_ms_(100.00%)_Space_40.7_MB_(12.56%)
77

88
public class Solution {
99
public int uniquePaths(int m, int n) {

‎src/main/java/g0001_0100/s0064_minimum_path_sum/Solution.java

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@
22

33
// #Medium #Top_100_Liked_Questions #Array #Dynamic_Programming #Matrix
44
// #Dynamic_Programming_I_Day_16 #Udemy_Dynamic_Programming #Big_O_Time_O(m*n)_Space_O(m*n)
5-
// #2023_08_11_Time_0_ms_(100.00%)_Space_44_MB_(58.56%)
5+
// #2024_11_11_Time_1_ms_(99.73%)_Space_47.5_MB_(44.29%)
66

77
public class Solution {
88
public int minPathSum(int[][] grid) {

‎src/main/java/g0001_0100/s0070_climbing_stairs/Solution.java

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
// #Easy #Top_100_Liked_Questions #Top_Interview_Questions #Dynamic_Programming #Math #Memoization
44
// #Algorithm_I_Day_12_Dynamic_Programming #Dynamic_Programming_I_Day_2
55
// #Level_1_Day_10_Dynamic_Programming #Udemy_Dynamic_Programming #Big_O_Time_O(n)_Space_O(n)
6-
// #2023_08_11_Time_0_ms_(100.00%)_Space_39.2_MB_(71.51%)
6+
// #2024_11_11_Time_0_ms_(100.00%)_Space_40.3_MB_(41.06%)
77

88
public class Solution {
99
public int climbStairs(int n) {

‎src/main/java/g0001_0100/s0072_edit_distance/Solution.java

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
// #Medium #Top_100_Liked_Questions #String #Dynamic_Programming
44
// #Algorithm_II_Day_18_Dynamic_Programming #Dynamic_Programming_I_Day_19
55
// #Udemy_Dynamic_Programming #Big_O_Time_O(n^2)_Space_O(n2)
6-
// #2023_08_11_Time_4_ms_(90.13%)_Space_41.8_MB_(99.78%)
6+
// #2024_11_11_Time_3_ms_(97.19%)_Space_43.2_MB_(98.23%)
77

88
@SuppressWarnings("java:S2234")
99
public class Solution {

‎src/main/java/g0001_0100/s0073_set_matrix_zeroes/Solution.java

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@
22

33
// #Medium #Top_100_Liked_Questions #Top_Interview_Questions #Array #Hash_Table #Matrix
44
// #Udemy_2D_Arrays/Matrix #Big_O_Time_O(m*n)_Space_O(1)
5-
// #2023_08_11_Time_1_ms_(79.07%)_Space_44.4_MB_(94.19%)
5+
// #2024_11_11_Time_0_ms_(100.00%)_Space_45.6_MB_(50.86%)
66

77
public class Solution {
88
// Approach: Use first row and first column for storing whether in future

‎src/main/java/g0001_0100/s0074_search_a_2d_matrix/Solution.java

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
// #Medium #Top_100_Liked_Questions #Array #Binary_Search #Matrix #Data_Structure_I_Day_5_Array
44
// #Algorithm_II_Day_1_Binary_Search #Binary_Search_I_Day_8 #Level_2_Day_8_Binary_Search
55
// #Udemy_2D_Arrays/Matrix #Big_O_Time_O(endRow+endCol)_Space_O(1)
6-
// #2023_08_11_Time_0_ms_(100.00%)_Space_40.9_MB_(71.91%)
6+
// #2024_11_11_Time_0_ms_(100.00%)_Space_42.2_MB_(40.02%)
77

88
public class Solution {
99
public boolean searchMatrix(int[][] matrix, int target) {

‎src/main/java/g0001_0100/s0075_sort_colors/Solution.java

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@
22

33
// #Medium #Top_100_Liked_Questions #Top_Interview_Questions #Array #Sorting #Two_Pointers
44
// #Data_Structure_II_Day_2_Array #Udemy_Arrays #Big_O_Time_O(n)_Space_O(1)
5-
// #2023_08_11_Time_0_ms_(100.00%)_Space_41_MB_(50.59%)
5+
// #2024_11_11_Time_0_ms_(100.00%)_Space_41.5_MB_(91.22%)
66

77
public class Solution {
88
public void sortColors(int[] nums) {

‎src/main/java/g0001_0100/s0076_minimum_window_substring/Solution.java

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@
22

33
// #Hard #Top_100_Liked_Questions #Top_Interview_Questions #String #Hash_Table #Sliding_Window
44
// #Level_2_Day_14_Sliding_Window/Two_Pointer #Big_O_Time_O(s.length())_Space_O(1)
5-
// #2023_08_11_Time_2_ms_(99.94%)_Space_43.6_MB_(93.87%)
5+
// #2024_11_11_Time_2_ms_(99.83%)_Space_44.5_MB_(89.46%)
66

77
public class Solution {
88
public String minWindow(String s, String t) {

‎src/main/java/g0001_0100/s0078_subsets/Solution.java

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@
22

33
// #Medium #Top_100_Liked_Questions #Top_Interview_Questions #Array #Bit_Manipulation #Backtracking
44
// #Algorithm_II_Day_9_Recursion_Backtracking #Udemy_Backtracking/Recursion
5-
// #Big_O_Time_O(2^n)_Space_O(n*2^n) #2023_08_11_Time_1_ms_(70.60%)_Space_41.8_MB_(71.73%)
5+
// #Big_O_Time_O(2^n)_Space_O(n*2^n) #2024_11_11_Time_0_ms_(100.00%)_Space_43_MB_(12.48%)
66

77
import java.util.ArrayList;
88
import java.util.List;

‎src/main/java/g0001_0100/s0079_word_search/Solution.java

Lines changed: 40 additions & 31 deletions
Original file line numberDiff line numberDiff line change
@@ -2,43 +2,52 @@
22

33
// #Medium #Top_100_Liked_Questions #Top_Interview_Questions #Array #Matrix #Backtracking
44
// #Algorithm_II_Day_11_Recursion_Backtracking #Big_O_Time_O(4^(m*n))_Space_O(m*n)
5-
// #2023_08_11_Time_157_ms_(78.97%)_Space_40.5_MB_(84.41%)
5+
// #2024_11_11_Time_64_ms_(98.51%)_Space_41.6_MB_(51.63%)
66

77
public class Solution {
8-
private boolean backtrace(
9-
char[][] board, boolean[][] visited, String word, int index, int x, int y) {
10-
if (index == word.length()) {
11-
return true;
12-
}
13-
if (x < 0 || x >= board.length || y < 0 || y >= board[0].length || visited[x][y]) {
14-
return false;
15-
}
16-
visited[x][y] = true;
17-
if (word.charAt(index) == board[x][y]) {
18-
boolean res =
19-
backtrace(board, visited, word, index + 1, x, y + 1)
20-
|| backtrace(board, visited, word, index + 1, x, y - 1)
21-
|| backtrace(board, visited, word, index + 1, x + 1, y)
22-
|| backtrace(board, visited, word, index + 1, x - 1, y);
23-
if (!res) {
24-
visited[x][y] = false;
25-
}
26-
return res;
27-
} else {
28-
visited[x][y] = false;
29-
return false;
30-
}
31-
}
8+
private boolean exists = false;
329

3310
public boolean exist(char[][] board, String word) {
34-
boolean[][] visited = new boolean[board.length][board[0].length];
35-
for (int i = 0; i < board.length; ++i) {
36-
for (int j = 0; j < board[0].length; ++j) {
37-
if (backtrace(board, visited, word, 0, i, j)) {
38-
return true;
11+
for (int i = 0; i < board.length; i++) {
12+
for (int j = 0; j < board[0].length; j++) {
13+
if (board[i][j] == word.charAt(0)) {
14+
dfs(board, word, 1, i, j);
3915
}
4016
}
4117
}
42-
return false;
18+
return exists;
19+
}
20+
21+
private void dfs(char[][] board, String word, int wordIndex, int i, int j) {
22+
if (wordIndex == word.length()) {
23+
exists = true;
24+
return;
25+
}
26+
char currentChar = board[i][j];
27+
char nextChar = word.charAt(wordIndex);
28+
if (i > 0 && board[i - 1][j] == nextChar) {
29+
// go up
30+
board[i][j] = '-';
31+
dfs(board, word, wordIndex + 1, i - 1, j);
32+
board[i][j] = currentChar;
33+
}
34+
if (j > 0 && board[i][j - 1] == nextChar) {
35+
// go left
36+
board[i][j] = '-';
37+
dfs(board, word, wordIndex + 1, i, j - 1);
38+
board[i][j] = currentChar;
39+
}
40+
if (i < board.length - 1 && board[i + 1][j] == nextChar) {
41+
// go down
42+
board[i][j] = '-';
43+
dfs(board, word, wordIndex + 1, i + 1, j);
44+
board[i][j] = currentChar;
45+
}
46+
if (j < board[0].length - 1 && board[i][j + 1] == nextChar) {
47+
// go right
48+
board[i][j] = '-';
49+
dfs(board, word, wordIndex + 1, i, j + 1);
50+
board[i][j] = currentChar;
51+
}
4352
}
4453
}

‎src/test/java/g0001_0100/s0049_group_anagrams/SolutionTest.java

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -12,9 +12,9 @@ class SolutionTest {
1212
@Test
1313
void groupAnagrams() {
1414
List<List<String>> expected = new ArrayList<>();
15+
expected.add(Arrays.asList("tan", "nat"));
1516
expected.add(Arrays.asList("eat", "tea", "ate"));
1617
expected.add(Arrays.asList("bat"));
17-
expected.add(Arrays.asList("tan", "nat"));
1818
List<List<String>> actual =
1919
new Solution()
2020
.groupAnagrams(new String[] {"eat", "tea", "tan", "ate", "nat", "bat"});

‎src/test/java/g0001_0100/s0051_n_queens/SolutionTest.java

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -14,8 +14,8 @@ void solveNQueens() {
1414
equalTo(
1515
ArrayUtils.getLists(
1616
new String[][] {
17-
{".Q..", "...Q", "Q...", "..Q."},
18-
{"..Q.", "Q...", "...Q", ".Q.."}
17+
{"..Q.", "Q...", "...Q", ".Q.."},
18+
{".Q..", "...Q", "Q...", "..Q."}
1919
})));
2020
}
2121

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