[topcoder]TopographicalImage

BFS。这里用了queue，以及在数据结构里存了上一个的高度。也可以递归调用完成BFS，在调用之前做判断：http://community.topcoder.com/stat?c=problem_solution&cr=9958883&rd=5856&pm=2932

import java.util.*;

public class TopographicalImage

{

    public int[] calcPeakAreas(String[] topoData)

    {

        int m = topoData.length;

        int n = topoData[0].length();

        ArrayList<Integer> ans = new ArrayList<Integer>();

        int total = 0;

        boolean[][] visited = new boolean[m][n];

        while (total < m * n)

        {

            int max = -1;

            Pair p = new Pair(0, 0, 0);

            for (int i = 0; i < m; i++)

            {

                for (int j = 0; j < n; j++)

                {

                    if (!visited[i][j] && topoData[i].charAt(j) > max)

                    {

                        max = topoData[i].charAt(j);

                        p.x = i;

                        p.y = j;

						p.lastHeight = max;

                    }

                }

            }

            Queue<Pair> queue = new LinkedList<Pair>();

            queue.add(p);

            int cnt = 0;

            while (queue.size() != 0)

            {

                Pair t = queue.poll();

				int h = topoData[t.x].charAt(t.y);

                if (!visited[t.x][t.y] &&  h <= t.lastHeight)

                {

                    visited[t.x][t.y] = true;

                    cnt++;

                    if (t.y + 1 < n) queue.add(new Pair(t.x, t.y + 1, h));

                    if (t.x + 1 < m) queue.add(new Pair(t.x + 1, t.y, h));

                    if (t.y - 1 >= 0) queue.add(new Pair(t.x, t.y - 1, h));

                    if (t.x - 1 >= 0) queue.add(new Pair(t.x - 1, t.y, h));

					if (t.x + 1 < m && t.y + 1 < n) queue.add(new Pair(t.x + 1, t.y + 1, h));

                    if (t.x + 1 < m && t.y - 1 >= 0) queue.add(new Pair(t.x + 1, t.y - 1, h));

                    if (t.x - 1 >= 0 && t.y - 1 >= 0) queue.add(new Pair(t.x - 1, t.y - 1, h));

                    if (t.x - 1 >= 0 && t.y + 1 < n) queue.add(new Pair(t.x - 1, t.y + 1, h));

                }

            }

            ans.add(cnt);

            total += cnt;

        }

		int[] res = new int[ans.size()];

		for (int i = 0; i < ans.size(); i++)

		{

			res[i] = ans.get(i);

		}

		return res;

    }

}

 

class Pair

{

    int x;

    int y;

	int lastHeight;

    public Pair(int _x, int _y, int _lastHeight)

    {

        x = _x;

        y = _y;

		lastHeight = _lastHeight;

    }

}