本篇内容介绍了“C++怎么实现螺旋矩阵”的有关知识,在实际案例的操作过程中,不少人都会遇到这样的困境,接下来就让小编带领大家学习一下如何处理这些情况吧!希望大家仔细阅读,能够学有所成!
螺旋矩阵
Given a positive integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.
Example:
Input: 3
Output:
[
[ 1, 2, 3 ],
[ 8, 9, 4 ],
[ 7, 6, 5 ]
]
此题跟之前那道 Spiral Matrix 本质上没什么区别,就相当于个类似逆运算的过程,这道题是要按螺旋的顺序来填数,由于给定矩形是个正方形,我们计算环数时用 n / 2 来计算,若n为奇数时,此时最中间的那个点没有被算在环数里,所以最后需要单独赋值,还是下标转换问题是难点,参考之前 Spiral Matrix 的讲解来转换下标吧,参见代码如下:
解法一:
class Solution {public: vector<vector<int>> generateMatrix(int n) { vector<vector<int>> res(n, vector<int>(n)); int val = 1, p = n; for (int i = 0; i < n / 2; ++i, p -= 2) { for (int col = i; col < i + p; ++col) res[i][col] = val++; for (int row = i + 1; row < i + p; ++row) res[row][i + p - 1] = val++; for (int col = i + p - 2; col >= i; --col) res[i + p - 1][col] = val++; for (int row = i + p - 2; row > i; --row) res[row][i] = val++; } if (n % 2 != 0) res[n / 2][n / 2] = val; return res; }};
当然我们也可以使用下面这种简化了坐标转换的方法,博主个人还是比较推崇下面这种解法,不容易出错,而且好理解,参见代码如下:
解法二:
class Solution {public: vector<vector<int>> generateMatrix(int n) { vector<vector<int>> res(n, vector<int>(n)); int up = 0, down = n - 1, left = 0, right = n - 1, val = 1; while (true) { for (int j = left; j <= right; ++j) res[up][j] = val++; if (++up > down) break; for (int i = up; i <= down; ++i) res[i][right] = val++; if (--right < left) break; for (int j = right; j >= left; --j) res[down][j] = val++; if (--down < up) break; for (int i = down; i >= up; --i) res[i][left] = val++; if (++left > right) break; } return res; }};
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