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7 files changed

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‎src/LeetcodeQuestions/SubsetSum.java‎

Lines changed: 46 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
11
package LeetcodeQuestions;
22

33
import java.util.ArrayList;
4+
import java.util.Arrays;
45
import java.util.List;
56

67
public class SubsetSum {
@@ -45,6 +46,51 @@ public static List<List<Integer>> combSum(int arr[], int tar) {
4546
}
4647

4748

49+
// Method 2------------>
50+
51+
public static void backtrack(List<List<Integer>> list, List<Integer> tempList, int[] nums, int remain,
52+
int start) {
53+
if (remain < 0)
54+
return;
55+
else if (remain == 0)
56+
list.add(new ArrayList<>(tempList));
57+
else {
58+
for (int i = start; i < nums.length; i++) {
59+
tempList.add(nums[i]);
60+
backtrack(list, tempList, nums, remain - nums[i], i); // not i + 1 because we can
61+
// reuse same elements
62+
tempList.remove(tempList.size() - 1);
63+
}
64+
}
65+
}
66+
67+
68+
// Method 2---> with duplicate values.. can't reuse same element
69+
public static void backtrack2(List<List<Integer>> list, List<Integer> tempList, int[] nums, int remain,
70+
int start) {
71+
if (remain < 0)
72+
return;
73+
else if (remain == 0)
74+
list.add(new ArrayList<>(tempList));
75+
else {
76+
for (int i = start; i < nums.length; i++) {
77+
if (i > start && nums[i] == nums[i - 1])
78+
continue; // skip duplicates
79+
tempList.add(nums[i]);
80+
backtrack2(list, tempList, nums, remain - nums[i], i + 1);
81+
tempList.remove(tempList.size() - 1);
82+
}
83+
}
84+
}
85+
86+
87+
public List<List<Integer>> helper2(int[] nums, int target) {
88+
List<List<Integer>> list = new ArrayList<>();
89+
Arrays.sort(nums);
90+
backtrack(list, new ArrayList<>(), nums, target, 0);
91+
return list;
92+
93+
}
4894

4995
public static void main(String[] args) {
5096

‎src/LeetcodeQuestions/palindromePartition.java‎

Lines changed: 47 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,47 @@
1+
package LeetcodeQuestions;
2+
3+
import java.util.ArrayList;
4+
import java.util.List;
5+
6+
// https://leetcode.com/problems/palindrome-partitioning/
7+
public class palindromePartition {
8+
9+
10+
public static List<List<String>> partition(String s) {
11+
List<List<String>> list = new ArrayList<>();
12+
backtrack(list, new ArrayList<>(), s, 0);
13+
return list;
14+
}
15+
16+
public static void backtrack(List<List<String>> list, List<String> tempList, String s,
17+
int start) {
18+
if (start == s.length())
19+
list.add(new ArrayList<>(tempList));
20+
else {
21+
for (int i = start; i < s.length(); i++) {
22+
if (isPalindrome(s, start, i)) {
23+
tempList.add(s.substring(start, i + 1));
24+
backtrack(list, tempList, s, i + 1);
25+
tempList.remove(tempList.size() - 1);
26+
}
27+
}
28+
}
29+
}
30+
31+
public static boolean isPalindrome(String s, int low, int high) {
32+
while (low < high)
33+
if (s.charAt(low++) != s.charAt(high--))
34+
return false;
35+
return true;
36+
}
37+
38+
39+
public static void main(String[] args) {
40+
41+
for (List<String> li : partition("aab")) {
42+
43+
System.out.println(li);
44+
}
45+
}
46+
47+
}

‎src/LeetcodeQuestions/permutations.java‎

Lines changed: 49 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -1,11 +1,12 @@
11
package LeetcodeQuestions;
22

33
import java.util.ArrayList;
4+
import java.util.Arrays;
45
import java.util.List;
56

67
// https://leetcode.com/problems/permutations/
78

8-
9+
910
// https://github.com/shashankch/DataStructures-Algo-Java/blob/master/src/PrepStringPermuteBacktrack.java
1011

1112
public class permutations {
@@ -27,7 +28,7 @@ public static void permute(int[] nums, int i, List<List<Integer>> list) {
2728

2829
}
2930

30-
public static void swap(int[] nums, int i, int j) {
31+
public static void swap(int[] nums, int i, int j) {
3132
int temp = nums[i];
3233
nums[i] = nums[j];
3334
nums[j] = temp;
@@ -42,15 +43,58 @@ public static List<List<Integer>> helper(int[] nums) {
4243

4344

4445
}
45-
46+
47+
48+
// Method 2-------------->
49+
50+
public static void backtrack(List<List<Integer>> list, List<Integer> tempList, int[] nums) {
51+
if (tempList.size() == nums.length) {
52+
list.add(new ArrayList<>(tempList));
53+
} else {
54+
for (int i = 0; i < nums.length; i++) {
55+
if (tempList.contains(nums[i]))
56+
continue; // element already exists, skip
57+
tempList.add(nums[i]);
58+
backtrack(list, tempList, nums);
59+
tempList.remove(tempList.size() - 1);
60+
}
61+
}
62+
}
63+
64+
// Method 2 with duplicate values...
65+
public static void backtrack2(List<List<Integer>> list, List<Integer> tempList, int[] nums,
66+
boolean[] used) {
67+
if (tempList.size() == nums.length) {
68+
list.add(new ArrayList<>(tempList));
69+
} else {
70+
for (int i = 0; i < nums.length; i++) {
71+
if (used[i] || i > 0 && nums[i] == nums[i - 1] && !used[i - 1])
72+
continue;
73+
used[i] = true;
74+
tempList.add(nums[i]);
75+
backtrack2(list, tempList, nums, used);
76+
used[i] = false;
77+
tempList.remove(tempList.size() - 1);
78+
}
79+
}
80+
}
81+
82+
83+
public List<List<Integer>> helper2(int[] nums) {
84+
List<List<Integer>> list = new ArrayList<>();
85+
Arrays.sort(nums); // sorting needed in duplicate values case
86+
backtrack2(list, new ArrayList<>(), nums, new boolean[nums.length]);
87+
return list;
88+
}
89+
4690

4791
public static void main(String[] args) {
48-
92+
4993
int arr[] = {1, 2, 3};
5094
for (List<Integer> li : helper(arr)) {
5195

5296
System.out.println(li);
53-
97+
5498
}
5599

56100
}

‎src/LeetcodeQuestions/subsets.java‎

Lines changed: 38 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
11
package LeetcodeQuestions;
22

33
import java.util.ArrayList;
4+
import java.util.Arrays;
45
import java.util.List;
56

67
public class subsets {
@@ -42,6 +43,7 @@ public static List<List<Integer>> helper(int arr[]) {
4243
return result;
4344
}
4445

46+
// Method 2----------->
4547
// O(N*2^N)
4648
public static List<List<Integer>> helper2(int arr[]) {
4749

@@ -64,6 +66,42 @@ public static List<List<Integer>> helper2(int arr[]) {
6466

6567
}
6668

69+
// Method 3--------->
70+
71+
public List<List<Integer>> helper3(int[] nums) {
72+
List<List<Integer>> list = new ArrayList<>();
73+
Arrays.sort(nums);
74+
backtrack(list, new ArrayList<>(), nums, 0);
75+
return list;
76+
}
77+
78+
public void backtrack(List<List<Integer>> list, List<Integer> tempList, int[] nums,
79+
int start) {
80+
list.add(new ArrayList<>(tempList));
81+
for (int i = start; i < nums.length; i++) {
82+
tempList.add(nums[i]);
83+
backtrack(list, tempList, nums, i + 1);
84+
tempList.remove(tempList.size() - 1);
85+
}
86+
}
87+
88+
// for arr containing duplicate values..
89+
public void backtrack2(List<List<Integer>> list, List<Integer> tempList, int[] nums,
90+
int start) {
91+
list.add(new ArrayList<>(tempList));
92+
for (int i = start; i < nums.length; i++) {
93+
if (i > start && nums[i] == nums[i - 1])
94+
continue; // skip duplicates
95+
tempList.add(nums[i]);
96+
backtrack2(list, tempList, nums, i + 1);
97+
tempList.remove(tempList.size() - 1);
98+
}
99+
}
100+
101+
102+
103+
104+
67105

68106
public static void main(String[] args) {
69107

‎src/arrays/PairSum.java‎

Lines changed: 33 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
33
import java.util.Arrays;
44

55
public class PairSum {
6-
public static void pairSum(int[] arr, int num) {
6+
public static void pairSum1(int[] arr, int num) {
77

88
Arrays.sort(arr);
99

@@ -33,4 +33,36 @@ public static void pairSum(int[] arr, int num) {
3333
}
3434

3535
}
36+
37+
38+
public static void pairSum2(int[] input, int x) {
39+
40+
for (int i = 0; i < input.length - 1; i++) {
41+
42+
for (int j = i + 1; j < input.length; j++)
43+
44+
{
45+
46+
if (input[i] + input[j] == x) {
47+
48+
if (input[i] < input[j]) {
49+
System.out.println(input[i] + " " + input[j]);
50+
} else {
51+
System.out.println(input[j] + " " + input[i]);
52+
}
53+
54+
}
55+
56+
57+
58+
}
59+
}
60+
61+
62+
63+
}
64+
65+
public static void main(String[] args) {
66+
67+
}
3668
}

‎src/arrays/sort01.java‎

Lines changed: 27 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,8 +1,34 @@
11

22
package arrays;
33

4-
public class sort01{
4+
public class sort01 {
55

6+
7+
public static void helper2(int[] arr) {
8+
9+
10+
int l = 0;
11+
int h = arr.length - 1;
12+
13+
while (l < h) {
14+
15+
16+
if (arr[l] == 0) {
17+
l++;
18+
} else if (arr[h] == 1) {
19+
h--;
20+
} else if (arr[l] == 1 && arr[h] == 0) {
21+
22+
int temp = arr[l];
23+
arr[l] = arr[h];
24+
arr[h] = temp;
25+
}
26+
27+
28+
29+
}
30+
31+
}
632

733
public static void main(String[] args) {
834

‎src/arrays/tripletsum.java‎

Lines changed: 26 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -65,6 +65,31 @@ public static void tripletfun(int arr[], int n, int x) {
6565

6666
}
6767

68+
public static void tripletfun2(int[] input, int x) {
69+
70+
Arrays.sort(input);
71+
for (int i = 0; i < input.length; i++) {
72+
73+
for (int j = i + 1; j < input.length; j++) {
74+
75+
for (int k = j + 1; k < input.length; k++) {
76+
77+
if (input[i] + input[j] + input[k] == x) {
78+
79+
System.out.println(input[i] + " " + input[j] + " " + input[k]);
80+
81+
}
82+
83+
84+
}
85+
}
86+
87+
88+
}
89+
90+
91+
}
92+
6893
public static void main(String[] args) {
6994

7095
Scanner sc = new Scanner(System.in);
@@ -83,4 +108,4 @@ public static void main(String[] args) {
83108

84109
}
85110

86-
}
111+
}

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