[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 ]

]

问题描述：给定一个整数n，生成一个方阵，它含有从1到n^2的元素，而且这些整数以向中间旋转的方式排列。

我采用的是最笨的办法，先来看外面一圈是如何计算的，第0行，从0～2依次是1～3，然后是第2列，第1个是4，然后是第2行，从2～0依次是5～7，然后是第0列，第1个是8。

class Solution {

public:

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

        // Note: The Solution object is instantiated only once and is reused by each test case.

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

        

        int i = 0, j = 0;

        int count = 1;

        int index = 0;

        int start = 0, end = n-1;

        while(count <= n*n) {

            for(i = index, j = start; j <= end && count <= n*n; j++)

                vec[i][j] = count++;



            for(j = n-1-index, i = start+1; i < end && count <= n*n; i++)

                vec[i][j] = count++;

 

            for(i = n-1-index, j = end; j >= start && count <= n*n; j--)

                vec[i][j] = count++;

 

            for(j = index, i = end-1; i >= start+1 && count <= n*n; i--)

                vec[i][j] = count++;



            index++;

            start++;

            end--;

        }



        return vec;  

    }

};