First missing positive integer in linear time and constant space
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This problem was asked by Stripe.
Given an array of integers, find the first missing positive integer in
linear time and constant space. In other words, find the lowest
positive integer that does not exist in the array. The array can
contain duplicates and negative numbers as well.
For example, the input [3, 4, -1, 1] should give 2. The input [1, 2,
0] should give 3.
You can modify the input array in-place.
class DailyCodingProblem5 {
public static void main(String args) {
int arr = { 3, 4, -1, 1 };
int res = solution(arr);
System.out.println(res);
int arr2 = { 1, 2, 0 };
res = solution(arr2);
System.out.println(res);
}
private static int solution(int arr) {
int n = arr.length;
int i = 0;
for (i = 0; i < n; i++) {
int val = arr[i];
if (val <= 0 || val > n)
continue;
while (val != arr[val - 1]) {
int nextval = arr[val - 1];
arr[val - 1] = val;
val = nextval;
if (val <= 0 || val > n) {
break;
}
}
}
for (i = 0; i < n; i++) {
if (arr[i] != i + 1) {
return i + 1;
}
}
return i;
}
}
How can i improve the above solution? Is there any improvements i can have in my code ?
java algorithm programming-challenge
asked 13 mins ago
Maclean PintoMaclean Pinto
1645
$endgroup$
add a comment |
$begingroup$
This problem was asked by Stripe.
Given an array of integers, find the first missing positive integer in
linear time and constant space. In other words, find the lowest
positive integer that does not exist in the array. The array can
contain duplicates and negative numbers as well.
For example, the input [3, 4, -1, 1] should give 2. The input [1, 2,
0] should give 3.
You can modify the input array in-place.
class DailyCodingProblem5 {
public static void main(String args) {
int arr = { 3, 4, -1, 1 };
int res = solution(arr);
System.out.println(res);
int arr2 = { 1, 2, 0 };
res = solution(arr2);
System.out.println(res);
}
private static int solution(int arr) {
int n = arr.length;
int i = 0;
for (i = 0; i < n; i++) {
int val = arr[i];
if (val <= 0 || val > n)
continue;
while (val != arr[val - 1]) {
int nextval = arr[val - 1];
arr[val - 1] = val;
val = nextval;
if (val <= 0 || val > n) {
break;
}
}
}
for (i = 0; i < n; i++) {
if (arr[i] != i + 1) {
return i + 1;
}
}
return i;
}
}
How can i improve the above solution? Is there any improvements i can have in my code ?
java algorithm programming-challenge
asked 13 mins ago
Maclean PintoMaclean Pinto
1645
$endgroup$
$begingroup$
your solution isn't in linear time.. yours is in $O(n² + n)$.. Should we now improve it to linear time or do you wan't only improvement feedback to you code :]
$endgroup$
– Roman
3 mins ago
$begingroup$
@Roman Could you substantiate your claim?
$endgroup$
– vnp
1 min ago
add a comment |
$begingroup$
This problem was asked by Stripe.
Given an array of integers, find the first missing positive integer in
linear time and constant space. In other words, find the lowest
positive integer that does not exist in the array. The array can
contain duplicates and negative numbers as well.
For example, the input [3, 4, -1, 1] should give 2. The input [1, 2,
0] should give 3.
You can modify the input array in-place.
class DailyCodingProblem5 {
public static void main(String args) {
int arr = { 3, 4, -1, 1 };
int res = solution(arr);
System.out.println(res);
int arr2 = { 1, 2, 0 };
res = solution(arr2);
System.out.println(res);
}
private static int solution(int arr) {
int n = arr.length;
int i = 0;
for (i = 0; i < n; i++) {
int val = arr[i];
if (val <= 0 || val > n)
continue;
while (val != arr[val - 1]) {
int nextval = arr[val - 1];
arr[val - 1] = val;
val = nextval;
if (val <= 0 || val > n) {
break;
}
}
}
for (i = 0; i < n; i++) {
if (arr[i] != i + 1) {
return i + 1;
}
}
return i;
}
}
How can i improve the above solution? Is there any improvements i can have in my code ?
java algorithm programming-challenge
asked 13 mins ago
Maclean PintoMaclean Pinto
1645
$endgroup$
This problem was asked by Stripe.
Given an array of integers, find the first missing positive integer in
linear time and constant space. In other words, find the lowest
positive integer that does not exist in the array. The array can
contain duplicates and negative numbers as well.
For example, the input [3, 4, -1, 1] should give 2. The input [1, 2,
0] should give 3.
You can modify the input array in-place.
class DailyCodingProblem5 {
public static void main(String args) {
int arr = { 3, 4, -1, 1 };
int res = solution(arr);
System.out.println(res);
int arr2 = { 1, 2, 0 };
res = solution(arr2);
System.out.println(res);
}
private static int solution(int arr) {
int n = arr.length;
int i = 0;
for (i = 0; i < n; i++) {
int val = arr[i];
if (val <= 0 || val > n)
continue;
while (val != arr[val - 1]) {
int nextval = arr[val - 1];
arr[val - 1] = val;
val = nextval;
if (val <= 0 || val > n) {
break;
}
}
}
for (i = 0; i < n; i++) {
if (arr[i] != i + 1) {
return i + 1;
}
}
return i;
}
}
How can i improve the above solution? Is there any improvements i can have in my code ?
java algorithm programming-challenge
java algorithm programming-challenge
asked 13 mins ago
Maclean PintoMaclean Pinto
1645
asked 13 mins ago
Maclean PintoMaclean Pinto
1645
asked 13 mins ago
Maclean PintoMaclean Pinto
1645
asked 13 mins ago
Maclean PintoMaclean Pinto
1645
asked 13 mins ago
Maclean PintoMaclean Pinto
1645
1645
$begingroup$
your solution isn't in linear time.. yours is in $O(n² + n)$.. Should we now improve it to linear time or do you wan't only improvement feedback to you code :]
$endgroup$
– Roman
3 mins ago
$begingroup$
@Roman Could you substantiate your claim?
$endgroup$
– vnp
1 min ago
add a comment |
$begingroup$
your solution isn't in linear time.. yours is in $O(n² + n)$.. Should we now improve it to linear time or do you wan't only improvement feedback to you code :]
$endgroup$
– Roman
3 mins ago
$begingroup$
@Roman Could you substantiate your claim?
$endgroup$
– vnp
1 min ago
$begingroup$
your solution isn't in linear time.. yours is in $O(n² + n)$.. Should we now improve it to linear time or do you wan't only improvement feedback to you code :]
$endgroup$
– Roman
3 mins ago
$begingroup$
your solution isn't in linear time.. yours is in $O(n² + n)$.. Should we now improve it to linear time or do you wan't only improvement feedback to you code :]
$endgroup$
– Roman
3 mins ago
$begingroup$
@Roman Could you substantiate your claim?
$endgroup$
– vnp
1 min ago
$begingroup$
@Roman Could you substantiate your claim?
$endgroup$
– vnp
1 min ago
add a comment |
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$begingroup$
your solution isn't in linear time.. yours is in $O(n² + n)$.. Should we now improve it to linear time or do you wan't only improvement feedback to you code :]
$endgroup$
– Roman
3 mins ago
$begingroup$
@Roman Could you substantiate your claim?
$endgroup$
– vnp
1 min ago