[LeetCode] Spiral Matrix II 螺旋矩阵之二-白红宇

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.

For example,

Given n = 3,

You should return the following matrix:

[ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ]]

此题跟之前那道本质上没什么区别，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，参考之前的讲解来转换下标吧，代码如下：

class Solution {public:    vector
      
       
         > generateMatrix(int n) {        vector
        
         
           > res(n, vector
          
           (n, 1));        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;    }};

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