LeetCode Algorithm 2326. Spiral Matrix IV

题目链接：2326. 螺旋矩阵 IV

Ideas

算法：边界压缩
数据结构：链表
思路：It seems that I have encountered similar problems when I first started learning algorithms,What rotates to print a matrix or something like that,similar to this.

1. 首先创建一个 m * n 的矩阵,默认用 -1 填充即可;
2. 定义up、down、left、right四个变量,represent the four boundaries of the matrix, respectively;
3. Traverse the linked list to fill in the matrix,After completing a row or column, the corresponding boundary is compressed,The order in which rows and columns are traversed is clockwise.

Code

C++

class Solution {
    
public:
    vector<vector<int>> spiralMatrix(int m, int n, ListNode* head) {
    
        vector<vector<int>> res(m, vector<int>(n, -1));
        int up = 0, down = m - 1, left = 0, right = n - 1;
        while (head) {
    
            // 1.从左向右,行不变列变
            for (int i = left; i < right + 1; i++) {
    
                res[up][i] = head->val;
                head = head->next;
                if (head == nullptr) return res;
            }
            if (up < down) up++;

            // 2.从上到下,列不变行变
            for (int i = up; i < down + 1; i++) {
    
                res[i][right] = head->val;
                head = head->next;
                if (head == nullptr) return res;
            }
            if (left < right) right--;

            // 3.从右向左,行不变列变
            for (int i = right; i > left - 1; i--) {
    
                res[down][i] = head->val;
                head = head->next;
                if (head == nullptr) return res;
            }
            if (up < down) down--;

            // 4.从下到上,列不变行变
            for (int i = down; i > up - 1; i--) {
    
                res[i][left] = head->val;
                head = head->next;
                if (head == nullptr) return res;
            }
            if (left < right) left++;
        }
        return res;
    }
};