zoukankan      html  css  js  c++  java
  • [Locked] Smallest Rectangle Enclosing Black Pixels

    An image is represented by a binary matrix with 0 as a white pixel and 1 as a black pixel. The black pixels are connected, i.e., there is only one black region. Pixels are connected horizontally and vertically. Given the location (x, y) of one of the black pixels, return the area of the smallest (axis-aligned) rectangle that encloses all black pixels.

    For example, given the following image:

    [
      "0010",
      "0110",
      "0100"
    ]
    

    and x = 0y = 2,

    Return 6.

    分析:

      典型Flood Fill泛洪算法的应用,从一个点扩展到整个区域。

    代码:

    class Solution {
    private:
        int xmin = INT_MAX, xmax = INT_MIN, ymin = INT_MAX, ymax = INT_MIN;
    public:
        inline void adjust(int i, int j) {
            xmin = min(xmin, i);
            xmax = max(xmax, i);
            ymin = min(ymin, j);
            ymax = max(ymax, j);
            return;
        }
        void dfs(vector<vector<int> > &matrix, int i, int j, vector<vector<bool> > visited) {
            if(!matrix[i][j] || visited[i][j])
                return;
            //调整最大边缘点
            adjust(i, j);
            visited[i][j] = true;
            dfs(matrix, i + 1, j, visited);
            dfs(matrix, i - 1, j, visited);
            dfs(matrix, i, j + 1, visited);
            dfs(matrix, i, j - 1, visited);
            visited[i][j] = false;
            return;
        }
        int minArea(vector<vector<int> > &matrix, int x, int y) {
            //设立岗哨,避免递归内部为了判断边界而产生大量开销
            matrix.insert(matrix.begin(), vector<int> (matrix[0].size(), 0));
            matrix.push_back(vector<int> (matrix[0].size(), 0));
            for(auto &m : matrix) {
                m.insert(m.begin(), 0);
                m.push_back(0);
            }
            //避免重复访问
            vector<vector<bool> > visited(matrix.size(), vector<bool> (matrix[0].size(), false));
            dfs(matrix, x + 1, y + 1, visited);
            return (ymax - ymin + 1) * (xmax - xmin + 1);
        }
    };
  • 相关阅读:
    [Android学习笔记]some tips
    ubuntu desktop 开机 连接网络
    ubuntn svn 安装 配置
    ubuntu 安装phpmyadmin
    ubuntu 安装flash插件
    ubuntu samba共享安装 配置
    ubuntu tengine 安装
    ubuntu vim之php函数提示
    ubuntu vim 插件安装
    nyoj-709-异 形 卵
  • 原文地址:https://www.cnblogs.com/littletail/p/5208054.html
Copyright © 2011-2022 走看看