leet code 54 第二次做数组顺时针展开

1， 将展开方向使用enum表示；

2，想好循环终止的条件-》转方向时下一次要访问的点越界或者已经访问过

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        vector<int> result;
        if (matrix.empty()) {
            return result;
        }
        if (matrix.front().empty()) {
            return result;
        }

        int m = matrix.size() - 1;
        int n = matrix.front().size() - 1;
        vector<vector<bool>> visted(matrix.size(), vector<bool>(matrix.front().size(), false));

        int i = 0;
        int j = 0;
        
        enum Direction {RIGHT, DOWN, LEFT, UP};
        Direction dir = Direction::RIGHT;

        while(1) {
            if (dir == Direction::RIGHT) {
                result.emplace_back(matrix[i][j]);
                visted[i][j] = true;
                // 到达右边界或者到达上一轮访问过的位置
                if (j == n || visted[i][j + 1] == true) {
                    if (i == m || visted[++i][j]) {
                        break;
                    }
                    dir = Direction::DOWN;
                }
                else if(visted[i][++j] == true) {
                    break;
                }
            }
            else if (dir == Direction::DOWN) {
                result.emplace_back(matrix[i][j]);
                visted[i][j] = true;
                if (i == m || visted[i + 1][j] == true) {
                    if (j == 0 || visted[i][--j]) {
                        break;
                    }
                    dir = Direction::LEFT;
                }
                else if(visted[++i][j] == true) {
                    break;
                }
            }
            else if (dir == Direction::LEFT) {
                result.emplace_back(matrix[i][j]);
                visted[i][j] = true;
                if (j == 0 || visted[i][j-1] == true) {
                    if (i == 0 || visted[--i][j]) {
                        break;
                    }
                    dir = Direction::UP;
                }
                else if (visted[i][--j] == true) {
                    break;
                }
            }
            else {
                result.emplace_back(matrix[i][j]);
                visted[i][j] = true;
                if (i == 0 || visted[i - 1][j] == true) {
                    if (j == n || visted[i][++j]) {
                        break;
                    }
                    dir = Direction::RIGHT;
                }
                else if (visted[--i][j] == true){
                    break;
                }
            }
        }
        return result;
    }
};