题解 | #回型矩阵#

#include <iostream>
using namespace std;
//利用边界条件之间的关系进行条件判断，赋值，分两步进行
//1.将方阵分为外层，内层
//2.对外层进行赋值，完成后，内层变为外层 ，重复
int main() {
    int n, up, down, right, left, count = 1;
    scanf("%d",&n);
    int map[n][n];
    up = 0, right = n - 1, left = 0, down = n - 1;
    while (up < down || left < right) {
        for (int i = left; i < right ; i++) {//上端赋值
            map[up][i] = count++;
        }
        for (int i = left; i < down ; i++) {//左侧赋值
            map[i][right] = count++;
        }
        for (int i = right ; i > left; i--) {//下端赋值
            map[down][i] = count++;
        }
        for (int i = down ; i > left; i--) {//右侧赋值
            map[i][left] = count++;
        }
        up++;			//将内层切换成外层
        down--;
        left++;
        right--;
    }
    if(left == right && up == down) map[up][down] = count;//对于奇数层数的矩阵，中间数需要另外赋值
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            cout << map[i][j] << ' ';
        }
        cout << endl;
    }
    return 0;
}