【leetcode】Spiral Matrix II

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 ]]

观察上述的矩阵，基本就是按顺序输出就可以了，注意二维vector的建立~

class Solution {public:    vector<vector<int> > generateMatrix(int n) {        vector<vector<int> > result(n, vector<int>(n));        int first=0,last=n-1;        int num=1;        while(first<last)        {            for(int i=first;i<last;i++) {result[first][i]=num;num++;}            for(int j=first;j<last;j++) {result[j][last]=num;num++;}            for(int i=last;i>first;i--) {result[last][i]=num;num++;}            for(int j=last;j>first;j--) {result[j][first]=num;num++;}            first++;            last--;        }        if(first==last)result[first][first]=num;        return result;    }};