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Palantir Coding Challenge Question
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import java.util.HashMap; | |
import java.util.Map; | |
import java.util.Scanner; | |
/** | |
* Credit for Algorithm from top answer in: | |
* http://stackoverflow.com/questions/7116438/algorithms-question-flipping-columns | |
* | |
* This problem is given to interview candidates in the screening process | |
* for Palantir Technologies. I've seen it through several different | |
* candidates. | |
* | |
* Given an n*m Matrix of 'P' and 'T' characters, find the maximum number | |
* of completely 'P' rows, after k column flips. | |
* | |
* A column flip consists of taking one column in the matrix, and inverting | |
* it's values (i.e. all 'P' to 'T' and all 'T' to 'P') | |
* | |
* Here is an example matrix: | |
* PPT | |
* TPT | |
* TTT | |
* | |
* if k = 1, the optimal solution is: | |
* PPP | |
* TPP | |
* TTP | |
* and it should output 1. | |
* | |
* The number of all 'P' rows is 1, once the algorithm completes. | |
* | |
* The input for the above test case would be: | |
* 3 3 | |
* PPT | |
* TPT | |
* TTT | |
* 1 | |
* | |
* The output would be: | |
* 1 | |
* | |
* @author Joseph Liccini | |
* | |
*/ | |
public class PalantirCodingChallenge { | |
public static void main(String[] args) { | |
Scanner sc = new Scanner(System.in); | |
int n = sc.nextInt(); | |
int m = sc.nextInt(); | |
char[][] matrix = new char[n][m]; | |
for (int i = 0; i < n; ++i) | |
matrix[i] = sc.next().toCharArray(); | |
int k = sc.nextInt(); | |
Map<String, Integer> map = new HashMap<String, Integer>(); | |
for (int i = 0; i < n; ++i) { | |
char[] row = matrix[i]; | |
int count = 0; | |
for (char c: row) | |
if (c == 'T') ++count; | |
if (count == k || (k - count >= 0 && (k - count) % 2 != 0)) { | |
String key = new String(row); | |
if (map.containsKey(key)) | |
map.put(key, map.get(key)+1); | |
else | |
map.put(key, 1); | |
} | |
} | |
int max = 0; | |
for (int value: map.values()) | |
max = Math.max(value, max); | |
System.out.println(max); | |
sc.close(); | |
} | |
} |
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I think;
(k - count) % 2 != 0) should be
(k - count) % 2 == 0)