JAVA（2021-11-27）leetcode每日一题----随机翻转矩阵

class Solution {
		
		HashMap map = new HashMap();
		Random ra = new Random(300);
		int m, n, cnt;

		public Solution(int m, int n) {
			this.m = m;
			this.n = n;
			this.cnt = m * n;
		}

		public int[] flip() {
			//在[0,cnt)取一个随机数，并给右边界-1
			int x = ra.nextInt(cnt--);
			
			int idx = map.getOrDefault(x, x);
			map.put(x, map.getOrDefault(cnt, cnt));
			return new int[] { idx / n, idx % n };
		}

		public void reset() {
			cnt = m * n;
			map.clear();
		}
	}