59. Spiral Matrix II

题目

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 ]
]

解析

class Solution_59 {
public:
    vector<vector<int> > generateMatrix(int n) {

        vector<vector<int>> vecs(n, vector<int>(n,1));
        
        int x0 = 0, y0 = 0;
        int x1 = n - 1, y1 = n - 1;

        int index = 0;
        while (x0<=x1&&y0<=y1)
        {
            for (int i = y0; i <= y1;i++)
            {
                vecs[x0][i] = ++index;
            }
            for (int i = x0 + 1; i <= x1;i++)
            {
                vecs[i][y1] = ++index;
            }
            for (int i = y1 - 1; i >= y0;i--)
            {
                vecs[x1][i] = ++index;
            }
            for (int i = x1 - 1; i > x0;i--)
            {
                vecs[i][y0] = ++index;
            }

            x0++, y0++;
            x1--, y1--;
        }
        
        return vecs;
    }
};

题目来源

• 59. Spiral Matrix II