Spiral Matrix II (Medium)

Description

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.

Analysis

跟前一题一样的。。稍微改一下就好了.直接模拟。。

My Solution

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//C++
class Solution {
public:
    vector<vector<int> > generateMatrix(int n) {
        vector<vector<int> >ans(n,vector<int>(n));
        int dx[] = {0,1,0,-1};
        int dy[] = {1,0,-1,0};
        int u = 0 ,d = n - 1 , l = 0, r = n - 1;
        int x = 0 , y = 0 , num = 1 , dir = 0;
        while(num<=n*n){
            if(x>=u&&y>=l&&x<=d&&y<=r){
                ans[x][y] = num;
                num++;
                x+=dx[dir];
                y+=dy[dir];
            }
            else{
                x-=dx[dir];
                y-=dy[dir];
                if(dir == 0)    u++;
                else if(dir == 1)    r--;
                else if(dir == 2)    d--;
                else l++;
                dir = (dir+1)%4;
                x+=dx[dir];
                y+=dy[dir];
            }
        }   
        return ans;
    }
};