[LeetCode 59] 螺旋矩阵 II

class Solution {
    public int[][] generateMatrix(int n) {
        int[][] res = new int[n][n];
        int left = 0,right = n - 1,top = 0,bottom = n - 1;
        int count = 0;
        while(count < n * n){
            //从左到右
            if(top <= bottom){
                for(int i = left;i <= right;i++){
                    count++;
                    res[top][i] = count;
                }
                top++;
            }

            //上到下
            if(left <= right){
                for(int i = top;i <= bottom;i++){
                    count++;
                    res[i][right] = count;
                }
                right--;
            }

            //右到左
            if(top <= bottom){
                for(int i = right;i >= left;i--){
                    count++;
                    res[bottom][i] = count;
                }
                bottom--;
            }

            //下到上
            if(left <= right){
                for(int i = bottom;i >= top;i--){
                    count++;
                    res[i][left] = count;
                }
                left++;
            }
        }
        return res;
    }
}