LeetCode 刷題記錄59. Spiral Matrix II

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

Example:

Input: 3
Output:
[
[ 1, 2, 3 ],
[ 8, 9, 4 ],
[ 7, 6, 5 ]
]
此題與https://blog.csdn.net/dldldl1994/article/details/102329861
思想一致
c++：

class Solution {
public:
    vector<vector<int>> generateMatrix(int n) {
        vector<vector<int>> res(n,vector<int>(n,0));
        
        int up = 0, down = n -1;
        int left = 0, right = n -1;
        int val = 1;
        while(true){
            for(int j = left; j <= right; ++j) res[up][j] = val++;
            if(++up > down) break;
            for(int i = up; i <= down; ++i) res[i][right] = val++;
            if(--right < left) break;
            for(int j = right; j >= left; --j) res[down][j]= val++;
            if(--down < up) break;
            for(int i = down; i >= up; --i) res[i][left] = val++;
            if(++left > right) break;
        }
        return res;
    }
};

java：

class Solution {
    public int[][] generateMatrix(int n) {
        int[][] res = new int[n][n];
        
        int up = 0, down = n -1;
        int left = 0, right = n -1;
        int val = 1;
        while(true){
            for(int j = left; j <= right; ++j) res[up][j] = val++;
            if(++up > down) break;
            for(int i = up; i <= down; ++i) res[i][right] = val++;
            if(--right < left) break;
            for(int j = right; j >= left; --j) res[down][j]= val++;
            if(--down < up) break;
            for(int i = down; i >= up; --i) res[i][left] = val++;
            if(++left > right) break;
        }
        return res;
    }
}

class Solution(object):
    def generateMatrix(self, n):
        """
        :type n: int
        :rtype: List[List[int]]
        """
        res = [[0 for i in xrange(n)] for j in xrange(n)]
        
        up = 0
        down = n -1
        left = 0
        right = n -1
        val = 1
        while True:
            for j in xrange(left,right+1): 
                res[up][j] = val
                val += 1
            up += 1
            if up > down: break
            for i  in xrange(up,down+1): 
                res[i][right] = val
                val += 1
            right -= 1
            if right < left: break
            for j in xrange(right,left-1,-1): 
                res[down][j]= val
                val += 1
            down -= 1
            if down < up: break
            for i in xrange(down, up-1,-1): 
                res[i][left] = val
                val += 1
            left += 1
            if left > right: break;
        
        return res