2021 阿里巴巴编程题
import java.util.*; import java.lang.*; public class Main { public static void main(String[] args) { Scanner sc = new Scanner(System.in); int t = sc.nextInt(); for (int k = 0; k < t; k++) { int n = sc.nextInt(); int[][] nums = new int[n][2]; for (int i = 0; i < n; i++) { nums[i][0] = sc.nextInt(); } for (int i = 0; i < n; i++) { nums[i][1] = sc.nextInt(); } Arrays.sort(nums, (o1, o2) -> o1[0]==o2[0]? o2[1]-o1[1]:o1[0]-o2[0]); System.out.println(solve(nums)); } } public static int solve(int[][] nums) { int n = nums.length; int[] dp = new int[n+1]; // dp[i]表示长度为i的LIS子序列最后一位的值 int maxLen = 1; dp[1] = nums[0][1]; for (int i = 1; i < n; i++) { if (nums[i][1] > dp[maxLen]) { maxLen++; dp[maxLen] = nums[i][1]; } else { int idx = find(dp, maxLen, nums[i][1]); dp[idx] = nums[i][1]; } } return maxLen; } // >= public static int find(int[] dp, int maxLen, int target) { int left = 1, right = maxLen; while (left <= right) { int mid = left + ((right - left) >> 1); if (dp[mid] < target) { left = mid + 1; } else { right = mid - 1; } } return left; } }
https://www.nowcoder.com/test/question/a55198d2e65746009110226f2f6c8533?pid=30440638&tid=52108831
import java.util.*; import java.lang.*; public class Main { static int[][] dirs = {{1,0}, {-1,0}, {0,1}, {0,-1}}; static class node { int x, y, cnt, used; node(int xx, int yy, int count, int num) { x = xx; y = yy; cnt = count; used = num; } } public static void main(String[] args) { Scanner sc = new Scanner(System.in); int n = sc.nextInt(); int m = sc.nextInt(); char[][] board = new char[n][m]; int sx = 0, sy = 0, ex = 0, ey = 0; for (int i = 0; i < n; i++) { String row = sc.next(); // 注意:不要用nextLine,next只取到有效字符 for (int j = 0; j < row.length(); j++) { board[i][j] = row.charAt(j); if (board[i][j] == 'S') { sx = i; sy = j; } if (board[i][j] == 'E') { ex = i; ey = j; } } } int[][] vis = new int[n][m]; Deque<node> que = new LinkedList<>(); que.offer(new node(sx, sy, 0, 5)); vis[sx][sy] = 1; boolean flag = false;; while (!que.isEmpty()) { node cur = que.poll(); if (cur.x == ex && cur.y == ey) { System.out.println(cur.cnt); flag = true; break; } for (int[] dir: dirs) { int xx = cur.x + dir[0], yy = cur.y + dir[1]; if (!inBoard(n, m, xx, yy) || board[xx][yy] == '#' || vis[xx][yy] == 1) continue; que.offer(new node(xx, yy, cur.cnt + 1, cur.used)); vis[xx][yy] = 1; } // 中心对称 int x1 = n -1 - cur.x, y1 = m - 1 - cur.y; if (cur.used > 0 && inBoard(n, m, x1, y1) && board[x1][y1] != '#' && vis[x1][y1] == 0) { que.offer(new node(x1, y1, cur.cnt + 1, cur.used-1)); vis[x1][y1] = 1; } } if (!flag) System.out.println(-1); } public static boolean inBoard(int n, int m, int x, int y) { if (x < 0 || x >= n || y < 0 || y >= m) return false; return true; } }
https://blog.csdn.net/qq_37702890/article/details/122846069?utm_medium=distribute.pc_relevant.none-task-blog-2~default~baidujs_title~default-0.pc_relevant_paycolumn_v3&spm=1001.2101.3001.4242.1&utm_relevant_index=2
有个物品可供选择,必须选择其中
个物品,请按字典序顺序输出所有选取方案的物品编号
import java.util.*; // dfs public class Main { public static void main(String[] args) { Scanner sc = new Scanner(System.in); int n = sc.nextInt(); int m = sc.nextInt(); List<Integer> path = new ArrayList<>(m); dfs(path, n, m, 1, 0); } public static void dfs(List<Integer> path, int n, int m, int index, int count) { if (count == m) { for (int i = 0; i < m; i++) { if (i != 0) System.out.print(" "); System.out.print(path.get(i)); } System.out.println(); return ; } if (index > n) return ; // 选择当前的数字 for (int i = index; i <= n; i++) { path.add(i); count++; dfs(path, n, m, i+1, count); path.remove(path.size() - 1); count--; } } }
关于BufferedReader
import java.util.*; import java.io.*; public class Main { public static void main(String[] args) throws Exception{ BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); int T = Integer.parseInt(br.readLine()); while (T-- > 0) { int n = Integer.parseInt(br.readLine()); String[] params = br.readLine().trim().split(" "); int[] costs = new int[n]; for (int i = 0; i < n; i++) costs[i] = Integer.parseInt(params[i]); Arrays.sort(costs); int ans = 0; while (n >= 4) { // 方案1. 最轻的人每次带一个让人过去; 方案2. 最轻的人和次最轻的人过去,最轻的人过来,最重和次重过去,次轻过来 ans += Math.min(2 * costs[0] + costs[n-1] + costs[n-2], costs[0] + 2*costs[1] + costs[n-1]); n -= 2; } if (n == 3) { ans += costs[0] + costs[1] + costs[2]; } else { ans += costs[1]; } System.out.println(ans); } } }
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