zoukankan      html  css  js  c++  java
  • [LeetCode] Max Area of Island

    Given a non-empty 2D array grid of 0's and 1's, an island is a group of 1's (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water.

    Find the maximum area of an island in the given 2D array. (If there is no island, the maximum area is 0.)

    Example 1:

    [[0,0,1,0,0,0,0,1,0,0,0,0,0],
     [0,0,0,0,0,0,0,1,1,1,0,0,0],
     [0,1,1,0,1,0,0,0,0,0,0,0,0],
     [0,1,0,0,1,1,0,0,1,0,1,0,0],
     [0,1,0,0,1,1,0,0,1,1,1,0,0],
     [0,0,0,0,0,0,0,0,0,0,1,0,0],
     [0,0,0,0,0,0,0,1,1,1,0,0,0],
     [0,0,0,0,0,0,0,1,1,0,0,0,0]]
    

    Given the above grid, return 6. Note the answer is not 11, because the island must be connected 4-directionally.

    Example 2:

    [[0,0,0,0,0,0,0,0]]

    Given the above grid, return 0.

    Note: The length of each dimension in the given grid does not exceed 50.

    [LeetCode] Number of Islands类似,稍加修改,只要在每次BFS时计算每个岛的面积即可。最后最大的面积。

    class Solution {
    public:
        int maxAreaOfIsland(vector<vector<int>>& grid) {
            if (grid.empty() || grid[0].empty())
                return 0;
            int maxArea = 0;
            const int M = grid.size();
            const int N = grid[0].size();
            vector<vector<bool>> visited(M, vector<bool>(N, false));
            for (int i = 0; i != M; i++) {
                for (int j = 0; j != N; j++) {
                    int area = 0;
                    if (!visited[i][j] && grid[i][j] == 1) {
                        maxAreaOflandCore(grid, visited, i, j, area);
                        maxArea = max(maxArea, area);
                    }
                }
            }
            return maxArea;
        }
        
        void maxAreaOflandCore(vector<vector<int>>& grid, vector<vector<bool>>& visited, int i, int j, int& area) {
            if (i >= 0 && i < grid.size() && j >= 0 && j < grid[0].size() && !visited[i][j] && grid[i][j] == 1) {
                area++;
                visited[i][j] = true;
                maxAreaOflandCore(grid, visited, i - 1, j, area);
                maxAreaOflandCore(grid, visited, i, j - 1, area);
                maxAreaOflandCore(grid, visited, i, j + 1, area);
                maxAreaOflandCore(grid, visited, i + 1, j, area);
            }
        }
    };
    // 26 ms
  • 相关阅读:
    Office 2007在安装过程中出错-解决办法
    Sql日期时间格式转换
    大型网站架构演变和知识体系
    作为一个web开发人员,哪些技术细节是在发布站点前你需要考虑到的
    Java 入门基础
    技术类面试、笔试题汇总
    怎样玩转千万级别的数据
    数据库性能优化:SQL索引
    最后一公里极速配送
    编辑-滴滴算法大赛算法解决过程
  • 原文地址:https://www.cnblogs.com/immjc/p/7645243.html
Copyright © 2011-2022 走看看