59. 螺旋矩阵 II：
给你一个正整数 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 n x n 正方形矩阵 matrix 。
样例 1：
输入：
n = 3
输出：
[[1,2,3],[8,9,4],[7,6,5]]
样例 2：
输入：
n = 1
输出：
[[1]]
提示：
- 1 <= n <= 20
分析：
- 面对这道算法题目，二当家的陷入了沉思。
- 可以每次循环移动一步，判断移到边界就变换方向。
- 也可以每次循环都换完4次方向，也就是完成一次顺时针，然后缩圈。
- 和 54. 螺旋矩阵 非常类似。
题解：
rust：
impl Solution {
pub fn generate_matrix(n: i32) -> Vec<Vec<i32>> {
let mut ans = vec![vec![0; n as usize]; n as usize];
let mut num = 0;
let (mut left, mut right, mut top, mut bottom) = (0, n as usize - 1, 0, n as usize - 1);
while left <= right && top <= bottom {
(left..right + 1).for_each(|column| {
num += 1;
ans[top][column] = num;
});
(top + 1..bottom + 1).for_each(|row| {
num += 1;
ans[row][right] = num;
});
if left < right && top < bottom {
(left..right).rev().for_each(|column| {
num += 1;
ans[bottom][column] = num;
});
(top + 1..bottom).rev().for_each(|row| {
num += 1;
ans[row][left] = num;
});
}
if right == 0 || bottom == 0 {
break;
}
left += 1;
right -= 1;
top += 1;
bottom -= 1;
}
return ans;
}
}
go：
func generateMatrix(n int) [][]int {
ans := make([][]int, n)
for i := range ans {
ans[i] = make([]int, n)
}
num := 0
left, right, top, bottom := 0, n-1, 0, n-1
for left <= right && top <= bottom {
for column := left; column <= right; column++ {
num++
ans[top][column] = num
}
for row := top + 1; row <= bottom; row++ {
num++
ans[row][right] = num
}
if left < right && top < bottom {
for column := right - 1; column >= left; column-- {
num++
ans[bottom][column] = num
}
for row := bottom - 1; row > top; row-- {
num++
ans[row][left] = num
}
}
left++
right--
top++
bottom--
}
return ans
}
c++：
class Solution {
public:
vector<vector<int>> generateMatrix(int n) {
vector<vector<int>> ans(n, vector<int>(n));
int num = 0;
int left = 0, right = n - 1, top = 0, bottom = n - 1;
while (left <= right && top <= bottom) {
for (int column = left; column <= right; ++column) {
ans[top][column] = ++num;
}
for (int row = top + 1; row <= bottom; ++row) {
ans[row][right] = ++num;
}
if (left < right && top < bottom) {
for (int column = right - 1; column >= left; --column) {
ans[bottom][column] = ++num;
}
for (int row = bottom - 1; row > top; --row) {
ans[row][left] = ++num;
}
}
++left;
--right;
++top;
--bottom;
}
return ans;
}
};
python：
class Solution:
def generateMatrix(self, n: int) -> List[List[int]]:
ans = [[0] * n for _ in range(n)]
num = 0
left, right, top, bottom = 0, n - 1, 0, n - 1
while left <= right and top <= bottom:
for column in range(left, right + 1):
num += 1
ans[top][column] = num
for row in range(top + 1, bottom + 1):
num += 1
ans[row][right] = num
if left < right and top < bottom:
for column in range(right - 1, left - 1, -1):
num += 1
ans[bottom][column] = num
for row in range(bottom - 1, top, -1):
num += 1
ans[row][left] = num
left, right, top, bottom = left + 1, right - 1, top + 1, bottom - 1
return ans
java：
class Solution {
public int[][] generateMatrix(int n) {
final int[][] ans = new int[n][n];
int num = 0;
int left = 0, right = n - 1, top = 0, bottom = n - 1;
while (left <= right && top <= bottom) {
for (int column = left; column <= right; ++column) {
ans[top][column] = ++num;
}
for (int row = top + 1; row <= bottom; ++row) {
ans[row][right] = ++num;
}
if (left < right && top < bottom) {
for (int column = right - 1; column >= left; --column) {
ans[bottom][column] = ++num;
}
for (int row = bottom - 1; row > top; --row) {
ans[row][left] = ++num;
}
}
++left;
--right;
++top;
--bottom;
}
return ans;
}
}
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