Cinte's Leetcode Record
0%

59. Spiral Matrix II

Posted on Edited on In Disqus:
Symbols count in article: 1k Reading time ≈ 1 mins.

59. Spiral Matrix II

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
class Solution {
public:
    vector<vector<int>> generateMatrix(int n) {
        vector<vector<int>> ret(n, vector<int>(n));
        int top = 0, bottom = n - 1, left = 0, right = n - 1;
        int num = 1;
        while(num <= n * n)
        {
            for(int i = left; i <= right; ++i)
                ret[top][i] = num++;
            ++top;
            for(int i = top; i <= bottom; ++i)
                ret[i][right] = num++;
            --right;
            for(int i = right; i >= left; --i)
                ret[bottom][i] = num++;
            --bottom;
            for(int i = bottom; i >= top; --i)
                ret[i][left] = num++;
            ++left;
        }
        return ret;
    }
};
2
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
class Solution {
public:
    vector<vector<int>> generateMatrix(int n) {
        vector<vector<int>> ret(n, vector<int>(n, 0));
        int dir[][2]{{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
        int d = 0;
        int m = 0, k = 0;
        for(int i = 1; i <= n * n; ++i)
        {
            ret[m][k] = i;
            int nextm = m + dir[d][0];
            int nextk = k + dir[d][1];
            if(nextm < 0 || nextm >= n || nextk < 0 || nextk >= n || ret[nextm][nextk] > 0)
                d = (d + 1) % 4;
            m += dir[d][0];
            k += dir[d][1];
        }
        return ret;
    }
};