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  • [LeetCode] Spiral Matrix

    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].

    开一个数组用来保存,之前这个单元是否被使用过,并配合边界判断,DFS,最后得出结果。空间复杂度O(n*m),时间O(n*m)

     1 class Solution {
     2 private:
     3     int step[4][2];
     4     vector<int> ret;
     5     bool canUse[100][100];
     6 public:
     7     void dfs(vector<vector<int> > &matrix, int direct, int x, int y)
     8     {
     9         for(int i = 0; i < 4; i++)
    10         {
    11             int j = (direct + i) % 4;
    12             int tx = x + step[j][0];
    13             int ty = y + step[j][1];
    14             if (0 <= tx && tx < matrix.size() && 0 <= ty && ty < matrix[0].size() && canUse[tx][ty])
    15             {
    16                 canUse[tx][ty] = false;
    17                 ret.push_back(matrix[tx][ty]);                
    18                 dfs(matrix, j, tx, ty);               
    19             }            
    20         }
    21     }
    22     
    23     vector<int> spiralOrder(vector<vector<int> > &matrix) {
    24         // Start typing your C/C++ solution below
    25         // DO NOT write int main() function
    26         step[0][0] = 0;
    27         step[0][1] = 1;
    28         step[1][0] = 1;
    29         step[1][1] = 0;
    30         step[2][0] = 0;
    31         step[2][1] = -1;
    32         step[3][0] = -1;
    33         step[3][1] = 0;
    34         ret.clear();
    35         memset(canUse, true, sizeof(canUse));
    36         dfs(matrix, 0, 0, -1);
    37         
    38         return ret;
    39     }
    40 };
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  • 原文地址:https://www.cnblogs.com/chkkch/p/2775708.html
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