[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;
    }
}