denis.zayats
BAN USER 1of 1 vote
AnswersYou have a plot with a limited amount of points on it.
Find the cluster of points, which contains the biggest amount of point grouped together.
Conditions:
The cluster means, that points are placed not farther than 5 units (Can be measured px, cm, etc.) between each other. The distance is calculated by wherex1x < 5
and
y1y < 5
The cluster should contain at least 3 points.
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If there are a few clusters with the same amount of points  return all of them.
Example:
The points are:
(15,116), (1345, 123), (456, 11), (34, 17), (19, 112), (556, 111), (454, 15), (12, 120).
In this case, the best cluster is (15,116), (19, 112), (12, 120) Report Duplicate  Flag  PURGE
Google SDE3 Algorithm  1of 1 vote
AnswersGiven a pyramid of consecutive integers:
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1
2 3
4 5 6
7 8 9 10
11 12 13 14 15
16 17 18 19 20 21
......
Find the sum of all the integers in the row number N.
For example:
The row #3: 4 + 5 + 6 = 15
The row #5: 11 + 12 + 13 + 14 + 15 = 65 Report Duplicate  Flag  PURGE
MobiCastle Software Engineer in Test  0of 0 votes
AnswersGiven the description of the ancient castle that contains years (e.g 910, 1111, 1560, 1809), centuries (X, XII, IX or 11th c, 15th c). The years and centuries might repeat many times.
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Assume that the centuries are equals(e.g XI = 1000, XV = 1400, 16th c = 1500)
Find the first historical mention about the castle in the text if you know that the very first mention could not be under 601 year. Report Duplicate  Flag  PURGE
MobiCastle Software Engineer  2of 2 votes
AnswersGiven the list of the numbers. In this list, there are the numbers from the Fibonacci sequence.
 denis.zayats in Switzerland
Write the algorithm that retrieves all the numbers which belong to the Fibonacci sequence of numbers. Report Duplicate  Flag  PURGE
MobiCastle Software Engineer Algorithm
We could represent the persons as the array of Qubits:
00: Celebrity  knows nobody in the room
01: No celebrity  knows only celebrity
10: No celebrity  knows everybody but no celebrity
11: No celebrity  knows the celebrity and everybody else
If we sort the array  then we know where to look for the celebrity.
Hint: use this method as a way of summing big numbers:
public String bigSum(String s1, String s2) {
int lengthS1 = s1.length();
int lengthS2 = s2.length();
int diff = Math.abs(lengthS1  lengthS2);
String prefix = repeatString("0", diff);
if (lengthS1 < lengthS2) {
s1 = prefix + s1;
} else if (lengthS2 < lengthS1) {
s2 = prefix + s2;
}
StringBuilder out = new StringBuilder();
int buf = 0;
for (int i = s1.length()  1; i >= 0; i) {
int n1 = Integer.parseInt(String.valueOf(s1.charAt(i)));
int n2 = Integer.parseInt(String.valueOf(s2.charAt(i)));
int sum = buf + n1 + n2;
buf = 0;
if (sum >= 10) {
sum = sum % 10;
buf++;
} else {
buf = 0;
}
if (buf > 0 && i == 0) {
out.insert(0, "1").insert(1, sum);
} else {
out.insert(0, sum);
}
}
return out.toString();
}

denis.zayats
March 06, 2018 Explain your answer in the code, please.
My explanation is:
1. Assume that we know that we need to start on the first line from left to right because we know that the last broken computer on the paired line (if to calculate from 1, not from 0) and it is closer to the right side.
2. It means that will be faster if we start the verification of the last line from the right side.
3. We have 5 rows of the 5 items in a row. The last broken computer is a first item in the 4th row. It means that 3*5 + 1 = 16.
The question is about possible combinations, not the permutations.
It means, that if we have a number 5  then possible combinations are:
1+1+1+1+1
2+1+1+1
2+2+1
3+1+1
4+1
Clarify the question, please.
Because, if the question is: is it possible to pair them (Put all the white sockets in the bucket#1 and all the black sockets in the bucket#2)? Then:
 if the number of socks is not paired {number} % 2 != 0  then the answer is immediately False.
 if the number is paired  we need to go through the list of the socks (could be both directional iteration) and put the socks on 2 different buckets. Once the number of socks (black or white) becomes bigger than half of all the socks  the answer is False.
 if the balancing of both lists works  then we will end the iteration with the balanced number of socks in both buckets.
If we need to differentiate by "left" and "right" for each color  then the flow is different.
This is an simple algorithm of how to convert Hex to Decimal and how to build RGB color, for example #4d4d4d = rgb(77, 77, 77).
public String convertColorHexToDecimal(String hex) {
StringBuilder result = new StringBuilder();
int counterDivider = 0;
StringBuilder buf = new StringBuilder();
for (int i = 0; i < hex.length(); i++) {
counterDivider ++;
buf.append(hex.charAt(i));
if (counterDivider == 2) {
result.append(convertHexToDecimal(buf.toString())).append(" ");
buf.delete(0, buf.length());
counterDivider = 0;
}
}
return result.toString();
}
public int convertHexToDecimal(String hex) {
int result = 0;
for (int i = 0; i < hex.length(); i++) {
result += Character.getNumericValue(hex.charAt(hex.length()  1  i)) * Math.pow(16, i);
}
return result;
}

denis.zayats
February 23, 2018 Complexity O(2*n/2) = O(n)
public String[] reverseArrayWithModification(String[] arr) {
String[] out = new String[arr.length  1];
int middle = arr.length / 2;
if (arr[middle].equals("&")) {
for (int i = 0; i < middle; i ++) {
out[i] = arr[arr.length  1  i];
}
for (int i = middle + 1; i <= 2 * middle; i ++) {
out[i  1] = arr[i  middle  1];
}
} else {
throw new IllegalArgumentException("Input array has no char '&'");
}
return out;
}

denis.zayats
February 22, 2018 Please, clarify the question.
Because, if we talk about Adjacency matrix for undirected graph  it's is a symmetric matrix, so, the answer will be always True.
ArrayList<int[]> coordinatesBrokenComputers = new ArrayList<>();
coordinatesBrokenComputers.add(new int[]{1,1});
coordinatesBrokenComputers.add(new int[]{1,4});
coordinatesBrokenComputers.add(new int[]{2,2});
coordinatesBrokenComputers.add(new int[]{3,4});
int[][] room = new int[][]{
{1,1,1,1,1},
{1,0,1,1,0},
{1,1,0,1,1},
{1,1,1,1,0},
{1,1,1,1,1}
};
assertEquals(16, coordinatesFounder.getLessAmountOfStepsToFindBrokenComputers(room, coordinatesBrokenComputers));
Implementation:
public int getLessAmountOfStepsToFindBrokenComputers(int[][] room, ArrayList<int[]> coordinatesBrokenComputers) {
int steps = 0;
int sizeOfBrokenComputers = coordinatesBrokenComputers.size();
for (int i = 0; i < room.length; i++) {
if (i % 2 == 0) {
for (int j = 0; j < room[i].length; j++) {
steps++;
if (room[i][j] == 0) {
sizeOfBrokenComputers;
if (sizeOfBrokenComputers == 0) {
return steps;
}
}
}
} else {
for (int j = room[i].length  1; j >= 0; j) {
steps++;
if (room[i][j] == 0) {
sizeOfBrokenComputers;
if (sizeOfBrokenComputers == 0) {
return steps;
}
}
}
}
}
return steps;
}

denis.zayats
February 19, 2018 Very short solution. It checks that 0 could be an island also if it's alone:
public boolean isAnIsland(int[][] matrix, int[] pointXY) {
assert pointXY.length == 2;
int x = pointXY[0];
int y = pointXY[1];
int value = matrix[x][y];
boolean top = x <= 0  (matrix[x  1][y] != value);
boolean bottom = x >= matrix.length  1  (matrix[x + 1][y] != value);
boolean left = y <= 0  (matrix[x][y  1] != value);
boolean right = y >= matrix[x].length  1  (matrix[x][y + 1] != value);
return top && bottom && left && right;
}
public int foundNumberOfIslands(int[][] matrix) {
int count = 0;
for (int i = 0; i < matrix.length; i++) {
for (int j = 0; j < matrix[i].length; j++) {
if (isAnIsland(matrix, new int[]{i, j})) {
count++;
System.out.println("Coordinates: " + i + ", " + j);
}
}
}
return count;
}

denis.zayats
February 19, 2018 Here is the multiplication. The method "bigSum" is described above.
The function works only with an equal Strings by length.
unit test:
bigMultipl("123456781234567812345678123456781231234567812345678123456781234567812345678123456781234567812345678123456781234567812345678123456781234567812345678123456781234567812345678123456781234567812345678456781234567812345678123456781234567812345678",
"123456781234567812345678123456781231234567812345678123456781234567812345678123456781234567812345678123456781234567812345678123456781234567812345678123456781234567812345678123456781234567812345678456781234567812345678123456781234567812345678"));
result =
15241566832799835131840019356816873129412161060136908261522059216750369293320360971620290100369704845365086870331252870116370369202120372405370527895373317370413557870939420377432620454710371351027673886100984519252301774947583571499390156842912823863303992974797473165550166654279282375988982091851404238129875577457087736154196977375165932083620904155824874754407079505654114672374342882186495595263426186618964206036665458836888572988923249505065691208988873673208352565279684
public String bigMultipl(String s1, String s2) {
LinkedList<String> list = new LinkedList<>();
int lengthS1 = s1.length();
int lengthS2 = s2.length();
int diff = Math.abs(lengthS1  lengthS2);
StringBuilder prefix = new StringBuilder();
for (int i = 0; i < diff; i++) {
prefix.append("0");
}
if (lengthS1 < lengthS2) {
s1 = prefix + s1;
} else if (lengthS2 < lengthS1) {
s2 = prefix + s2;
}
for (int i = s1.length()  1; i >= 0; i ) {
int buf = 0;
String tempSum = "";
for (int j = s2.length()  1; j >= 0; j ) {
int n1 = Integer.parseInt(String.valueOf(s1.charAt(i)));
int n2 = Integer.parseInt(String.valueOf(s2.charAt(j)));
int sum = buf + n1 * n2;
buf = 0;
if (sum >= 10) {
buf += sum / 10;
sum = sum % 10;
} else {
buf = 0;
}
tempSum = String.valueOf(sum) + tempSum;
}
if (buf > 0) {
list.add(buf + tempSum);
} else {
list.add(tempSum);
}
}
String sum = "";
for (int i = 0; i < list.size(); i ++) {
sum = bigSum(sum, list.get(i) + repeatString("0", i));
}
if (sum.startsWith("0")) {
sum = "1" + sum;
}
return sum;
}

denis.zayats
February 13, 2018 Steps:
1. Find the biggest 10^n number before "number"
2. Put into array 10^0 ... 10^n. We have smth like [1, 10, 100, 1000]
3. Print all the combinations
Exclude the steps if any of the preconditions are known already.
Continue to the answer above.
Tested with the UT:
assertEquals("0", codeBase.bigSum("909876545678909876878765546789765490987654567890987687876554678976546789909876545678909876878765546789765467890876545678908765457890087654567890876545789067899098765456789098768787655467897654678908765456789087654578900876545678908765457890", "909876545678909876878765546789765490987654567890987687876554678976546789909876545678909876878765546789765467890876545678908765457890087654567890876545789067899098765456789098768787655445678908765457890"));
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 denis.zayats March 13, 2018But this is not a question for the interview. Or, probably, if the person has the imagination at least how to start and what is expected as a final implementation.