Trapping Rain Water II

最新推荐文章于 2023-11-12 11:41:49 发布

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本文介绍了一种使用优先队列实现的雨水捕捉算法。该算法通过将地图边界上的高度加入优先队列，并逐步填充内部区域来计算可以捕捉多少雨水。具体步骤包括初始化队列、更新已访问标记、比较周围单元格高度等。

用优先队列，把边沿的墙全加进去，然后从最低的开始，看四周要不要补水。其他的和第一题很像

public class Solution {
    class cell implements Comparable{
        int x;
        int y;
        int height;

        public cell(int x, int y, int height) {
            this.x = x;
            this.y = y;
            this.height = height;
        }
        public int getX() {
            return x;
        }

        public void setX(int x) {
            this.x = x;
        }

        public int getY() {
            return y;
        }

        public void setY(int y) {
            this.y = y;
        }

        public int getHeight() {
            return height;
        }

        public void setHeight(int height) {
            this.height = height;
        }

        @Override
        public int compareTo( Object o) {
            cell oo = (cell) o;
            return height-((cell) o).getHeight();
        }
    }
    public int trapRainWater(int[][] heightMap) {
        int width = heightMap.length;
        if(width<=0)return 0;
        int length = heightMap[0].length;
        boolean [][]visted = new boolean[width][length];
        PriorityQueue<cell> priorityQueue = new PriorityQueue<>();
        if (width == 0 || length == 0)return 0;
        for (int i=0;i<width;i++){
            visted[i][length-1] = true;
            visted[i][0] = true;
            priorityQueue.add(new cell(length-1,i,heightMap[i][length-1]));
            priorityQueue.add(new cell(0,i,heightMap[i][0]));
        }
        for (int i=0;i<length;i++){
            visted[width-1][i] = true;
            visted[0][i] =true;
            priorityQueue.add(new cell(i,width-1,heightMap[width-1][i]));
            priorityQueue.add(new cell(i,0,heightMap[0][i]));
        }
        int res = 0;
        int[][] fangxiang = {{0,1},{0,-1},{-1,0},{1,0}};

        while (!priorityQueue.isEmpty()){
            cell ce = priorityQueue.poll();
            //System.out.println("height:"+ce.getHeight());
            for (int i=0;i<fangxiang.length;i++){
                int dx = ce.getX()+fangxiang[i][0];
                int dy = ce.getY()+fangxiang[i][1];
                if (dx>=0&&dx<length&&dy>=0&&dy<width) {
                    if(!visted[dy][dx]){
                        cell newCell = new cell(dx, dy, heightMap[dy][dx]);
                        visted[dy][dx] = true;
                        if (ce.compareTo(newCell)>0){
                            res+=ce.compareTo(newCell);
                           // System.out.println("res:"+res);
                            newCell.setHeight(ce.getHeight());
                            priorityQueue.add(newCell);
                            continue;

                        }else {
                            priorityQueue.add(newCell);
                        }
                    }
                }
            }

        }
        return res;

    }
}