Datawhale-LeetCode编程实践组队学习Task07

59. 螺旋矩阵 II

class Solution {
public:
    vector<vector<int>> generateMatrix(int n) {
        vector<vector<int>> res(n, vector<int>(n, 0));
        if (n == 0) return res;
        int num = 1;
        int left = 0, right = n - 1;
        int low = 0, hight = n - 1;
        while (left <= right && low <= hight) {
            for (int i = left; i <= right; i++) {
                res[low][i] = num++;
            }
            low++;
            if (low > hight) break;
            for (int i = low;i <=hight; i++ ) {
                res[i][right] = num++;
            }
            right--;
            if (right < left) break; 
            for (int i = right;i >=left;i--) {
                res[hight][i] = num++;
            }
            hight--;
            for (int i = hight;i >= low; i--) {
                res[i][left] = num++;
            }
            left++;
        }
        return res;
    }
};

61. 旋转链表

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* rotateRight(ListNode* head, int k) {
        if(!head) return NULL;
        int n=0;
        for(auto p=head;p;p=p->next) n++;
        k%=n;
        auto first=head,second=head;
        while(k--){
            first=first->next;
        }
        while(first->next){
            first=first->next;
            second=second->next;
        }
        first->next=head;
        head=second->next;
        second->next=NULL;
        return head;
    }
};

54. 螺旋矩阵

class Solution {
private:
    static constexpr int directions[4][2] = {
   
   {0, 1}, {1, 0}, {0, -1}, {-1, 0}};
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        if (matrix.size() == 0 || matrix[0].size() == 0) {
            return {};
        }
        
        int rows = matrix.size(), columns = matrix[0].size();
        vector<vector<bool>> visited(rows, vector<bool>(columns));
        int total = rows * columns;
        vector<int> order(total);

        int row = 0, column = 0;
        int directionIndex = 0;
        for (int i = 0; i < total; i++) {
            order[i] = matrix[row][column];
            visited[row][column] = true;
            int nextRow = row + directions[directionIndex][0], nextColumn = column + directions[directionIndex][1];
            if (nextRow < 0 || nextRow >= rows || nextColumn < 0 || nextColumn >= columns || visited[nextRow][nextColumn]) {
                directionIndex = (directionIndex + 1) % 4;
            }
            row += directions[directionIndex][0];
            column += directions[directionIndex][1];
        }
        return order;
    }
};