TopcoderArchiveVisit Topcoder
SRM5 Nov 2008
SRM 424

BestRoads

Problem statement, definition, constraints, and public examples.

Problem Statement

There are N cities numbered 0 to N-1. The j-th character of the i-th element of roads is 'Y' if there is a bidirectional road between cities i and j, and 'N' otherwise.
The road connecting cities A and B, where A < B, has a higher priority than the road connecting cities C and D, where C < D, if either A < C or (A = C and B < D). A set of roads is a list of one or more roads sorted from highest to lowest priority. A set S1 has a higher priority than set S2 if road S1[i] has a higher priority than road S2[i], where i is the earliest index at which the two sets differ. A set of roads is called connected if there's a path between any pair of cities containing only the roads from this set.
Your task is to find the connected set with the highest priority containing exactly M roads. Return a int[] where the i-th element is the number of roads in that set containing city i as an endpoint. Return an empty int[] if there is no such set.

Definition

Class:
BestRoads
Method:
numberOfRoads
Parameters:
String[], int
Returns:
int[]
Method signature:
int[] numberOfRoads(String[] roads, int M)
(be sure your method is public)

Constraints

  • roads will contain between 1 and 50 elements, inclusive.
  • M will be between N-1 and 1,000, inclusive, where N is the number of elements in roads.
  • Each element of roads will contain exactly N characters 'Y' or 'N', where N is the number of elements in roads.
  • For each i and j roads[i][j] will be equal to roads[j][i].
  • For each i roads[i][i] will be equal to 'N'.

Examples

  1. {"NYYYY","YNYYY","YYNYY","YYYNY","YYYYN"}
    10
    Returns: {4, 4, 4, 4, 4 }
    All roads should be selected.
  2. {"NYY","YNY","YYN"}
    2
    Returns: {2, 1, 1 }
    The set must contain roads 0-1 and 0-2.
  3. {"NYNNY","YNNNY","NNNNN","NNNNY","YYNYN"}
    4
    Returns: { }
    City 2 can not be connected to others.
  4. {"NYYNYYYN","YNNNNYYN","YNNNYNNN","NNNNNNYY","YNYNNNNN","YYNNNNYY","YYNYNYNY","NNNYNYYN"}
    10
    Returns: {5, 3, 2, 2, 2, 2, 3, 1 }
  5. {"NNYY","NNYY","YYNN","YYNN"}
    5
    Returns: { }
    There are totally 4 roads, so we can't choose 5 of them.
Back to all problems