59.螺旋矩阵II

class Solution {
    public int[][] generateMatrix(int n) {
        int[][] res = new int[n][n];
        int count = 1;
        int left = 0,right = n-1,top = 0,bottom = n -1;
        while(left <= right && top <= bottom){
            for(int col = left;col <= right;col++){ //从左往右
                res[top][col] = count;
                count++;
            }
            top++;
            for(int row = top ;row <= bottom;row++){
                res[row][right] = count; //从上到下
                count++;
            }
            right--;
             //从右往左
            for(int col = right ;col >= left;col--){
                res[bottom][col] = count; 
                count++;
            }
            bottom--;
            //从下往上
            for(int row = bottom ;row >= top;row--){
                res[row][left] = count;
                count++;
            }
            left++;
        }
        return res;
    }
}