classSolution{public:
vector<vector<int>>generateMatrix(int n){
vector<vector<int>>res(n, vector<int>(n,0));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;}};