From 4c12cfd6d538f04d291ca08beb3bfef3d65c33cf Mon Sep 17 00:00:00 2001 From: algorithmzuo Date: Sat, 10 Jun 2023 18:30:05 +0800 Subject: [PATCH] modify code --- .../Code04_CutOffTreesForGolfEvent.java | 167 ++++++++++++------ 1 file changed, 117 insertions(+), 50 deletions(-) diff --git a/算法周更班/class_2021_12_3_week/Code04_CutOffTreesForGolfEvent.java b/算法周更班/class_2021_12_3_week/Code04_CutOffTreesForGolfEvent.java index 87cd3a5..f17d5b2 100644 --- a/算法周更班/class_2021_12_3_week/Code04_CutOffTreesForGolfEvent.java +++ b/算法周更班/class_2021_12_3_week/Code04_CutOffTreesForGolfEvent.java @@ -1,74 +1,141 @@ package class_2021_12_3_week; -import java.util.ArrayList; -import java.util.LinkedList; +import java.util.Arrays; import java.util.List; +// leetcode增加了新的数据 +// 导致原来的实现不通过了 +// 一怒之下，做了各种优化 +// 思路完全和课上讲的一样，就是实现完全重来了 +// 目前打败100%的人 // 测试链接 : https://leetcode.com/problems/cut-off-trees-for-golf-event/ public class Code04_CutOffTreesForGolfEvent { + public static int MAXN = 51; + public static int MAXM = 51; + public static int LIMIT = MAXN * MAXM; + public static int[][] f = new int[MAXN][MAXM]; + public static int[][] arr = new int[LIMIT][3]; + public static int[] move = new int[] { 1, 0, -1, 0, 1 }; + public static int n, m; + + // 为了快，手撸双端队列 + public static int[][] deque = new int[LIMIT][3]; + // 双端队列的头、尾、大小 + public static int l, r, size; + + // 初始化双端队列 + public static void buildDeque() { + l = -1; + r = -1; + size = 0; + } + + // 双端队列从头部弹出 + public static int[] pollFirst() { + int[] ans = deque[l]; + if (l < LIMIT - 1) { + l++; + } else { + l = 0; + } + size--; + if (size == 0) { + l = r = -1; + } + return ans; + } + + // 双端队列从头部加入 + public static void offerFirst(int x, int y, int d) { + if (l == -1) { + deque[0][0] = x; + deque[0][1] = y; + deque[0][2] = d; + l = r = 0; + } else { + int fill = l == 0 ? (LIMIT - 1) : (l - 1); + deque[fill][0] = x; + deque[fill][1] = y; + deque[fill][2] = d; + l = fill; + } + size++; + } + + // 双端队列从尾部加入 + public static void offerLast(int x, int y, int d) { + if (l == -1) { + deque[0][0] = x; + deque[0][1] = y; + deque[0][2] = d; + l = r = 0; + } else { + int fill = (r == LIMIT - 1) ? 0 : (r + 1); + deque[fill][0] = x; + deque[fill][1] = y; + deque[fill][2] = d; + r = fill; + } + size++; + } + public static int cutOffTree(List> forest) { - int n = forest.size(); - int m = forest.get(0).size(); - // [ [3,5,2], [1,9,4] , [2,6,10] ] - // 低 中 高 - ArrayList cells = new ArrayList<>(); + n = forest.size(); + m = forest.get(0).size(); + int cnt = 0; for (int i = 0; i < n; i++) { for (int j = 0; j < m; j++) { - int val = forest.get(i).get(j); - if (val > 1) { - cells.add(new int[] { i, j, val }); + int value = forest.get(i).get(j); + f[i][j] = value > 0 ? 1 : 0; + if (value > 1) { + arr[cnt][0] = value; + arr[cnt][1] = i; + arr[cnt++][2] = j; } } } - cells.sort((a, b) -> a[2] - b[2]); - int ans = 0, lastR = 0, lastC = 0; - for (int[] cell : cells) { - int step = bestWalk(forest, lastR, lastC, cell[0], cell[1]); + Arrays.sort(arr, 0, cnt, (a, b) -> a[0] - b[0]); + int ans = 0; + for (int i = 0, x = 0, y = 0, block = 2; i < cnt; i++, block++) { + int toX = arr[i][1]; + int toY = arr[i][2]; + int step = walk(x, y, toX, toY, block); if (step == -1) { return -1; } ans += step; - lastR = cell[0]; - lastC = cell[1]; - forest.get(lastR).set(lastC, 1); + x = toX; + y = toY; } return ans; } - public static int[] next = { -1, 0, 1, 0, -1 }; - - // 0 1 2 3 4 - // i - // 行 + next[i-1] - // 列 + next[i] - // i == 1 -> 上 - // i == 2 -> 右 - // i == 3 -> 下 - // i == 4 -> 左 - public static int bestWalk(List> forest, int sr, int sc, int tr, int tc) { - int n = forest.size(); - int m = forest.get(0).size(); - boolean[][] seen = new boolean[n][m]; - LinkedList deque = new LinkedList<>(); - deque.offerFirst(new int[] { 0, sr, sc }); - while (!deque.isEmpty()) { - int[] cur = deque.pollFirst(); - int step = cur[0], r = cur[1], c = cur[2]; - if (r == tr && c == tc) { - return step; - } - seen[r][c] = true; - for (int i = 1; i < 5; i++) { // (r,c) 上下左右，全试试！ - int nr = r + next[i - 1]; - int nc = c + next[i]; - if (nr >= 0 && nr < n && nc >= 0 && nc < m && !seen[nr][nc] && forest.get(nr).get(nc) > 0) { - int[] move = { step + 1, nr, nc }; - // 更近的话 - if ((i == 1 && r > tr) || (i == 2 && c < tc) || (i == 3 && r < tr) || (i == 4 && c > tc)) { - deque.offerFirst(move); - } else { // 更远的话，放到尾部！ - deque.offerLast(move); + public static int walk(int a, int b, int c, int d, int block) { + buildDeque(); + offerFirst(a, b, 0); + while (size > 0) { + int[] cur = pollFirst(); + int x = cur[0]; + int y = cur[1]; + int distance = cur[2]; + if (f[x][y] != block) { + f[x][y] = block; + if (x == c && y == d) { + return distance; + } + for (int i = 1; i < 5; i++) { + int nextX = x + move[i]; + int nextY = y + move[i - 1]; + if (nextX >= 0 && nextX < n && nextY >= 0 && nextY < m && f[nextX][nextY] != 0 + && f[nextX][nextY] != block) { + if ((i == 1 && y < d) || (i == 2 && x > c) || (i == 3 && y > d) || (i == 4 && x < c)) { + // 离的更近 + offerFirst(nextX, nextY, distance + 1); + } else { + // 离的更远 + offerLast(nextX, nextY, distance + 1); + } } } }