LeetCode-Spiral Matrix

标签：leetcode   matrix   spiral matrix   

题目链接：https://oj.leetcode.com/problems/spiral-matrix/

题目内容：

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].

解题思路：运用了verilog状态机的思想，定义了一个state，进行状态的判断；状态1，从左到右，状态2，从上到下，状态3，从右到左，状态4，从下 到 上。（注意下，容器为空时的判断。）

     <pre name="code" class="cpp">  int m = matrix.size();
       vector<int> answers;
       if(m == 0) return answers ;

           不要写成，下面这种情况，会报错的。

     int m = matrix.size();
     int n = matrix[0].size();
       vector<int> answers;
       if(m == 0) return answers ;
      

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int> > &matrix) {
       int m = matrix.size();
       vector<int> answers;
       if(m == 0) return answers ;
       int n = matrix[0].size();
       int s[m][n];

       for(size_t i = 0; i != m; i++)
         for(size_t j = 0; j != n; j++)
             s[i][j] = 0;

       int  state = 1;
       int k = 0;
       int l = 0;
       int num = 0;
       while(num < m*n ) {
        if(state == 1) {  //left to right
          if(s[k][l] != 1 && l != n) {
             answers.push_back(matrix[k][l]);
             num ++;
             s[k][l] = 1;
             l++;
          } else {
              l--;
              k++;
              state=2;
          }
        } else if(state == 2) { //top to down
            if(s[k][l] != 1 && k != m) {
             answers.push_back(matrix[k][l]);
             num ++;
             s[k][l] = 1;
             k++;
            }
            else {
              k--;
              l--;
              state =3;
            }
        } else if(state == 3) { //right  to left
            if(s[k][l] != 1 && l != -1) {
             answers.push_back(matrix[k][l]);
             num ++;
             s[k][l] = 1;
             l--;
            }
            else {
              l++;
              k--;
              state =4;
            }
        } else if(state == 4) { //down to top
            if(s[k][l] != 1 && k != 0) {
             answers.push_back(matrix[k][l]);
             num ++;
             s[k][l] = 1;
             k--;
            }
            else {
              k++;
              l++;
              state =1;
            }
        }

       }
    return answers;
    }
};

LeetCode-Spiral Matrix

标签：leetcode   matrix   spiral matrix   

原文地址：http://blog.csdn.net/vanish_dust/article/details/42985599