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package class35;
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import java.util.PriorityQueue;
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// 来自网易
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// map[i][j] == 0，代表(i,j)是海洋，渡过的话代价是2
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// map[i][j] == 1，代表(i,j)是陆地，渡过的话代价是1
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// map[i][j] == 2，代表(i,j)是障碍，无法渡过
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// 每一步上、下、左、右都能走，返回从左上角走到右下角最小代价是多少，如果无法到达返回-1
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public class Code04_WalkToEnd {
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public static int minCost(int[][] map) {
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if (map[0][0] == 2) {
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return -1;
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}
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int n = map.length;
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int m = map[0].length;
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PriorityQueue<Node> heap = new PriorityQueue<>((a, b) -> a.cost - b.cost);
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boolean[][] visited = new boolean[n][m];
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add(map, 0, 0, 0, heap, visited);
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while (!heap.isEmpty()) {
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Node cur = heap.poll();
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if (cur.row == n - 1 && cur.col == m - 1) {
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return cur.cost;
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}
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add(map, cur.row - 1, cur.col, cur.cost, heap, visited);
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add(map, cur.row + 1, cur.col, cur.cost, heap, visited);
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add(map, cur.row, cur.col - 1, cur.cost, heap, visited);
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add(map, cur.row, cur.col + 1, cur.cost, heap, visited);
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}
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return -1;
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}
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public static void add(int[][] m, int i, int j, int pre, PriorityQueue<Node> heap, boolean[][] visited) {
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if (i >= 0 && i < m.length && j >= 0 && j < m[0].length && m[i][j] != 2 && !visited[i][j]) {
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heap.add(new Node(i, j, pre + (m[i][j] == 0 ? 2 : 1)));
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visited[i][j] = true;
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}
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}
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public static class Node {
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public int row;
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public int col;
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public int cost;
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public Node(int a, int b, int c) {
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row = a;
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col = b;
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cost = c;
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}
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}
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}
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