LeetCode_Spiral Matrix II

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 ]

]

　　

class Solution {

public:

    vector<vector<int> > generateMatrix(int n) {

        // Start typing your C/C++ solution below

        // DO NOT write int main() function

        vector<vector<int>> res(n,vector<int>(n));

        

        int lays = (n+1)/2;

        bool single = n%2;

        int num = 1;

        for(int lay = 0; lay < lays; lay ++){

        

            int topRow = lay;

            int rightColumn = n - 1 - lay;

            

            //process the top

            for(int i = lay; i <= rightColumn; i++)

                  res[topRow][i] = num++;

                  

            //process the right Column

            for(int i = lay+1; i <= rightColumn ;i++)

                  res[i][rightColumn] = num++;

                  

            if(lay == lays -1 && single )

                    continue;

                    

            //process the bottom 

            for(int i = rightColumn - 1; i>= lay; i--)

                  res[rightColumn][i] = num++;

                  

            for(int i = rightColumn - 1; i> lay ;i--)

                 res[i][lay] = num++;

        

        }

        

        return res;

    }

};