题解 | 校门外的树
校门外的树
https://www.nowcoder.com/practice/0e8cfc82936048769af45967f3c4ef7e
L, M = list(map(int, input().split()))
arr = [1] * (L + 1)
for i in range(M):
a, b = list(map(int, input().split()))
for j in range(a, b + 1):
arr[j] = 0
print(sum(arr))
哈希表解决这个问题
