LeetCode54/59 Spiral Matrix I/II

一：Spiral Matrix I

題目：

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].

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

分析：看代碼，四個while循環形成一個大圈

class Solution {
public:
    void dfs(int xi, int yi, const int &m, const int &n, vector > &matrix, vector &result, int **visited){
        visited[xi][yi] = 1;
        result.push_back(matrix[xi][yi]);
        while(yi+1 < n && !visited[xi][yi+1]){  // 四個while循環剛好跑了大正圈
            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 spiralOrder(vector > &matrix) {
        vector 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;
        
        
    }
};

題目：

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

For example,
Given n = 3,

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

class Solution {
public:
    void dfs(int xi, int yi, const int &n, vector > &result, int &value){
        result[xi][yi] = value++;
         while(yi+1 < n && !result[xi][yi+1]){  // 四個while循環剛好跑了大正圈
            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 > generateMatrix(int n) {
        vector >result;
        if(n == 0) return result;
        for(int i = 0; i < n; i++){  // 初始化result
            vector temp(n, 0);
            result.push_back(temp);
        }
        int value = 1;
        dfs(0,0, n, result, value);
        return result;
        
    }
};