Created
December 16, 2019 22:43
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Find the common base path of a list of file paths
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//package ; | |
import java.nio.file.Path; | |
import java.nio.file.Paths; | |
import java.util.List; | |
/** | |
* @see <a href="https://www.geeksforgeeks.org/longest-common-prefix-using-binary-search/">Longest | |
* Common Prefix using Binary Search</a> | |
*/ | |
public class BasePath { | |
private List<Path> list = new java.util.ArrayList<>(); | |
private int minLength = Integer.MAX_VALUE; | |
public void add(String first, String... more) { | |
add(Paths.get(first, more)); | |
} | |
public void add(Path path) { | |
list.add(path); | |
if (path.getNameCount() < minLength) { | |
minLength = path.getNameCount(); | |
} | |
} | |
public String find() { | |
if (list.isEmpty()) { | |
return ""; | |
} | |
Path[] paths = list.toArray(new Path[list.size()]); | |
int low = minLength, high = paths.length - 1; | |
while (low <= high) { | |
int mid = low + (high - low) / 2; | |
if (startWith(paths, low, mid)) { | |
low = mid + 1; | |
} else { | |
high = mid - 1; | |
} | |
} | |
return (low == 0) ? "" : paths[0].subpath(0, low).toString(); | |
} | |
private static boolean startWith(Path[] paths, int start, int end) { | |
Path prefix = paths[0]; | |
for (int i = 1, n = paths.length; i < n; i++) { | |
Path str = paths[i]; | |
for (int j = start; j <= end; j++) { | |
if (!str.getName(j).equals(prefix.getName(j))) { | |
return false; | |
} | |
} | |
} | |
return true; | |
} | |
public void clear() { | |
list.clear(); | |
minLength = Integer.MAX_VALUE; | |
} | |
} |
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