leetcode 59. 螺旋矩阵 II(Spiral Matrix II)

佚名 6年前 (2019-04-22) 随笔 1082人围观抢沙发百度已收录

题目描述：

给定一个正整数 n，生成一个包含 1 到 n² 所有元素，且元素按顺时针顺序螺旋排列的正方形矩阵。

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示例:

输入: 3
输出:
[
 [ 1, 2, 3 ],
 [ 8, 9, 4 ],
 [ 7, 6, 5 ]
]

解法：

class Solution {
public:
    vector<vector<int>> generateMatrix(int n) {
        int val = 1;
        int top = n*n;
        bool right = true, left = false, up = false, down = false;
        int max_x = n-1, min_x = 1;
        int max_y = n-1, min_y = 0;
        int dx = 0, dy = 1;
        int x = 0, y = -1;
        vector<vector<int>> res(n, vector<int>(n, 0));
        while(val <= top){
            x += dx;
            y += dy;
            res[x][y] = val;
            if(right){
                if(y == max_y){
                    right = false;
                    down = true;
                    dx = 1;
                    dy = 0;
                    max_y--;
                }
            }else if(down){
                if(x == max_x){
                    down = false;
                    left = true;
                    dx = 0;
                    dy = -1;
                    max_x--;
                }
            }else if(left){
                if(y == min_y){
                    left = false;
                    up = true;
                    dx = -1;
                    dy = 0;
                    min_y++;
                }
            }else if(up){
                if(x == min_x){
                    up = false;
                    right = true;
                    dx = 0;
                    dy = 1;
                    min_x++;
                }
            }
            val++;
        }
        return res;
    }
};