/*
 * @lc app=leetcode id=407 lang=java
 *
 * [407] Trapping Rain Water II
 */

// @lc code=start
class Solution {
    public int trapRainWater(int[][] heightMap) {
        PriorityQueue<Node> pq = new PriorityQueue<>((a, b)->{
            return a.h - b.h;
        });
        boolean[][] visited = visited(heightMap);
        pushBorders(heightMap, visited, pq);
        int[][] dirs = new int[][] {
            new int[] {1, 0},
            new int[] {-1, 0},
            new int[] {0, 1},
            new int[] {0,-1}
        };
        int cap = 0;
        while(!pq.isEmpty()) {
            Node cur = pq.poll();
            int x, y;
            for(int i=0; i<dirs.length; i++) {
                x = cur.r + dirs[i][0];
                y = cur.c + dirs[i][1];
                if(x >= 0 && x < heightMap.length && y >= 0 && y < heightMap[0].length  && !visited[x][y]) {
                    visited[x][y] = true;
                    int curh = heightMap[x][y];
                    if(heightMap[x][y] < cur.h) {
                        cap += cur.h - heightMap[x][y];
                        curh = cur.h;
                    }
                    pq.add(new Node(x, y, curh));
                }
            }
        }
        return cap;
    }


    private void pushBorders(int[][] hm, boolean[][] visited, PriorityQueue<Node> pq) {
        int r = hm.length, c = hm[0].length;
        for(int i=0;i<r;i++) {
            visited[i][0] = true;
            visited[i][c-1] = true;
            pq.add(new Node(i, 0, hm[i][0]));
            pq.add(new Node(i, c-1, hm[i][c-1]));
        }
        for(int i=0;i<c;i++) {
            if(!visited[0][i]) {
                visited[0][i] = true;
                pq.add(new Node(0, i, hm[0][i]));
            }
            if(!visited[r-1][i]) {
                visited[r-1][i] = true;
                pq.add(new Node(r-1, i, hm[r-1][i]));
            }
        }
    }

    private boolean[][] visited(int[][] heightMap) {
        boolean[][] v = new boolean[heightMap.length][heightMap[0].length];
        for(int i=0; i<v.length; i++) {
            for(int j=0;j<v[0].length;j++) {
                v[i][j] = false;
            }
        }
        return v;
    } 

    static class Node {
        int r, c, h;

        public Node(int r, int c, int h) {
            this.r = r;
            this.c = c;
            this.h = h;
        }
    }
}
// @lc code=end

// 12 13 1  12
// 13 4  13 12
// 13 8  10 12
// 12 13 12 12
// 13 13 13 13

// 0  0  0  0
// 0  9  0  0
// 0  4  2  0
// 0  0  0  0
// 0  0  0  0