LeetCode 885. 螺旋矩阵 III

示例 1：
输入：R = 1, C = 4, r0 = 0, c0 = 0
输出：[[0,0],[0,1],[0,2],[0,3]]

示例 2：
输入：R = 5, C = 6, r0 = 1, c0 = 4
输出：[[1,4],[1,5],[2,5],[2,4],[2,3],[1,3],[0,3],[0,4],[0,5],
[3,5],[3,4],[3,3],[3,2],[2,2],[1,2],[0,2],[4,5],[4,4],[4,3],
[4,2],[4,1],[3,1],[2,1],[1,1],[0,1],[4,0],[3,0],[2,0],[1,0],[0,0]]

提示：
1 <= R <= 100
1 <= C <= 100
0 <= r0 < R
0 <= c0 < C

class Solution {
public:
    vector<vector<int>> spiralMatrixIII(int R, int C, int r0, int c0) {
    	vector<vector<int>> dir = {{0,1},{1,0},{0,-1},{-1,0}};
    	int steps = 1, step, count = 1, k = 0, delta = 0;
    	vector<vector<int>> ans = {{r0,c0}};//初始为1个
    	while(count < R*C)
    	{
    		step = steps;//步长
    		while(step--)
    		{
    			r0 += dir[k][0];
    			c0 += dir[k][1];
    			if(r0>=0&& r0<R && c0>=0&&c0<C)
    			{
    				ans.push_back({r0,c0});
                    // cout << r0 << " " << c0 << endl;
    				count++;
    			}
    		}
    		k = (k+1)%4;//换方向
    		delta++;
    		if(delta%2==0)
    		{
    			delta = 0;
    			steps++;//每两次增加步长1格
    		}
    	}
    	return ans;
    }
};