LeetCode54/59 Spiral Matrix I/II

一：Spiral Matrix I

题目：

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

For example,
Given the following matrix:

[ [ 1, 2, 3 ], [ 4, 5, 6 ], [ 7, 8, 9 ]]

You should return [1,2,3,6,9,8,7,4,5].

链接：https://leetcode.com/problems/spiral-matrix/

分析：看代码，四个while循环形成一个大圈

class Solution {public:    void dfs(int xi, int yi, const int &m, const int &n, vector<vector<int> > &matrix, vector<int> &result, int **visited){        visited[xi][yi] = 1;        result.push_back(matrix[xi][yi]);        while(yi+1 < n && !visited[xi][yi+1]){  // 四个while循环刚好跑了大正圈            result.push_back(matrix[xi][yi+1]);            visited[xi][yi+1] = 1;            yi = yi+1;        }        while(xi+1 < m && !visited[xi+1][yi]){            result.push_back(matrix[xi+1][yi]);            visited[xi+1][yi] = 1;            xi = xi +1;        }        while(yi-1 >=0 && !visited[xi][yi-1]){            result.push_back(matrix[xi][yi-1]);            visited[xi][yi-1] = 1;            yi = yi-1;        }         while(xi-1 >=0 && !visited[xi-1][yi]){            result.push_back(matrix[xi-1][yi]);            visited[xi-1][yi] = 1;            xi = xi-1;        }        if(yi+1 < n && !visited[xi][yi+1]) dfs(xi, yi+1, m, n, matrix, result, visited);    }    vector<int> spiralOrder(vector<vector<int> > &matrix) {        vector<int> result;        int m = matrix.size();        if(m == 0) return result;                int n = matrix[0].size();        int **visited= new int*[m];        for(int i = 0; i < m; i++){            visited[i] = new int[n];            memset(visited[i], 0, sizeof(int)*n);        }        dfs(0, 0, m, n, matrix, result, visited);                for(int i = 0; i < m; i++)            delete [] visited[i];        delete []visited;        return result;                    }};

二：Spiral Matrix II

题目：

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.

For example,
Given n = 3,

You should return the following matrix:

[ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ]]

链接：https://leetcode.com/problems/spiral-matrix-ii/

class Solution {public:    void dfs(int xi, int yi, const int &n, vector<vector<int> > &result, int &value){        result[xi][yi] = value++;         while(yi+1 < n && !result[xi][yi+1]){  // 四个while循环刚好跑了大正圈            result[xi][yi+1] = value++;            yi = yi+1;        }        while(xi+1 < n && !result[xi+1][yi]){              result[xi+1][yi] = value++;            xi = xi+1;        }        while(yi-1 >= 0 && !result[xi][yi-1]){              result[xi][yi-1] = value++;            yi = yi-1;        }        while(xi-1 >= 0 && !result[xi-1][yi]){              result[xi-1][yi] = value++;            xi = xi-1;        }        if(yi+1 < n && !result[xi][yi+1]) dfs(xi, yi+1, n, result, value);    }        vector<vector<int> > generateMatrix(int n) {        vector<vector<int> >result;        if(n == 0) return result;        for(int i = 0; i < n; i++){  // 初始化result            vector<int> temp(n, 0);            result.push_back(temp);        }        int value = 1;        dfs(0,0, n, result, value);        return result;            }};