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].

题意：将数组环形遍历。

思路：将右，下，左，上连成环后，遍历，注意范围。

class Solution {public:    vector<int> spiralOrder(vector<vector<int> > &matrix) {        vector<int> ans;        if (matrix.empty())             return ans;        int n = matrix.size(), m = matrix[0].size();        int vis[1000][1000];        memset(vis, 0, sizeof(vis));        int dx[4] = {0, 1, 0, -1};        int dy[4] = {1, 0, -1, 0};        int dir = 0, x = 0, y = 0;        for (int i = 0; i < n*m; i++) {            ans.push_back(matrix[x][y]);            vis[x][y] = 1;            if (x+dx[dir] == n || x+dx[dir] < 0 ||                 y+dy[dir] == m || y+dy[dir] < 0 ||                 vis[x+dx[dir]][y+dy[dir]]) {                    dir = (dir == 3) ? 0 : dir+1;            }            x += dx[dir];            y += dy[dir];        }         return ans;    }};