59. 螺旋矩阵 II

class Solution:
    def generateMatrix(self, n: int) -> List[List[int]]:
        res = [[0] * n for _ in range(n)]
        num = 1
        m1, m2 = 0, n - 1
        while m1 < m2:
            for j in range(m1, m2):
                res[m1][j] = num
                num += 1
            for i in range(m1, m2):
                res[i][m2] = num
                num += 1
            for j in range(m2, m1, -1):
                res[m2][j] = num
                num += 1
            for i in range(m2, m1, -1):
                res[i][m1] = num
                num += 1
            m1 += 1
            m2 -= 1
        if m1 == m2:
            res[m1][m1] = num
        return res

class Solution {
    public int[][] generateMatrix(int n) {
        int[][] res = new int[n][n];
        int num = 1;
        int m1 = 0, m2 = n - 1;
        while (m1 < m2) {
            for (int j = m1; j < m2; ++j) {
                res[m1][j] = num++;
            }
            for (int i = m1; i < m2; ++i) {
                res[i][m2] = num++;
            }
            for (int j = m2; j > m1; --j) {
                res[m2][j] = num++;
            }
            for (int i = m2; i > m1; --i) {
                res[i][m1] = num++;
            }
            ++m1;
            --m2;
        }
        if (m1 == m2) {
            res[m1][m1] = num;
        }

        return res;
    }
}

function generateMatrix(n: number): number[][] {
    let ans = Array.from({ length: n }, v => new Array(n));
    let dir = [
        [0, 1],
        [1, 0],
        [0, -1],
        [-1, 0],
    ];
    let i = 0,
        j = 0;
    for (let cnt = 1, k = 0; cnt <= n * n; cnt++) {
        ans[i][j] = cnt;
        let x = i + dir[k][0],
            y = j + dir[k][1];
        if (x < 0 || x == n || y < 0 || y == n || ans[x][y]) {
            k = (k + 1) % 4;
            (x = i + dir[k][0]), (y = j + dir[k][1]);
        }
        (i = x), (j = y);
    }
    return ans;
}

function generateMatrix(n: number): number[][] {
    const res = new Array(n).fill(0).map(() => new Array(n).fill(0));
    let num = 1;
    for (let i = 0; i < Math.floor(n / 2); i++) {
        for (let j = i; j < n - i - 1; j++) {
            res[i][j] = num++;
        }
        for (let j = i; j < n - i - 1; j++) {
            res[j][n - i - 1] = num++;
        }
        for (let j = i; j < n - i - 1; j++) {
            res[n - i - 1][n - j - 1] = num++;
        }
        for (let j = i; j < n - i - 1; j++) {
            res[n - j - 1][i] = num++;
        }
    }
    if (n % 2 === 1) {
        res[n >> 1][n >> 1] = num;
    }
    return res;
}

class Solution {
public:
    vector<vector<int>> generateMatrix(int n) {
        vector<vector<int>> res(n, vector<int>(n, 0));
        int num = 1;
        int m1 = 0, m2 = n - 1;
        while (m1 < m2) {
            for (int j = m1; j < m2; ++j) {
                res[m1][j] = num++;
            }
            for (int i = m1; i < m2; ++i) {
                res[i][m2] = num++;
            }
            for (int j = m2; j > m1; --j) {
                res[m2][j] = num++;
            }
            for (int i = m2; i > m1; --i) {
                res[i][m1] = num++;
            }
            ++m1;
            --m2;
        }
        if (m1 == m2) {
            res[m1][m1] = num;
        }
        return res;
    }
};

impl Solution {
    pub fn generate_matrix(n: i32) -> Vec<Vec<i32>> {
        let n = n as usize;
        let mut res = vec![vec![0; n]; n];
        let mut num = 1;
        for i in 0..n / 2 {
            for j in i..n - i - 1 {
                res[i][j] = num;
                num += 1;
            }
            for j in i..n - i - 1 {
                res[j][n - i - 1] = num;
                num += 1;
            }
            for j in i..n - i - 1 {
                res[n - i - 1][n - j - 1] = num;
                num += 1;
            }
            for j in i..n - i - 1 {
                res[n - j - 1][i] = num;
                num += 1;
            }
        }
        if n % 2 == 1 {
            res[n >> 1][n >> 1] = num;
        }
        res
    }
}

func generateMatrix(n int) [][]int {
	res := make([][]int, n)
	for i := range res {
		res[i] = make([]int, n)
	}
	elem := 1
	top, bottom, left, right := 0, n-1, 0, n-1
	for elem <= n*n {
		for i := left; i <= right; i++ {
			res[top][i], elem = elem, elem+1
		}
		top++
		for i := top; i <= bottom; i++ {
			res[i][right], elem = elem, elem+1
		}
		right--
		if top <= bottom {
			for i := right; i >= left; i-- {
				res[bottom][i], elem = elem, elem+1
			}
			bottom--
		}
		if left <= right {
			for i := bottom; i >= top; i-- {
				res[i][left], elem = elem, elem+1
			}
			left++
		}
	}
	return res
}