CF954F.Runner's Problem
普及/提高-
通过率:0%
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题目描述
You are running through a rectangular field. This field can be represented as a matrix with 3 rows and m columns. (i,j) denotes a cell belonging to i -th row and j -th column.
You start in (2,1) and have to end your path in (2,m) . From the cell (i,j) you may advance to:
- (i−1,j+1) — only if i>1 ,
- (i,j+1) , or
- (i+1,j+1) — only if i<3 .
However, there are n obstacles blocking your path. k -th obstacle is denoted by three integers ak , lk and rk , and it forbids entering any cell (ak,j) such that lk<=j<=rk .
You have to calculate the number of different paths from (2,1) to (2,m) , and print it modulo 109+7 .
输入格式
The first line contains two integers n and m ( 1<=n<=104 , 3<=m<=1018 ) — the number of obstacles and the number of columns in the matrix, respectively.
Then n lines follow, each containing three integers ak , lk and rk ( 1<=ak<=3 , 2<=lk<=rk<=m−1 ) denoting an obstacle blocking every cell (ak,j) such that lk<=j<=rk . Some cells may be blocked by multiple obstacles.
输出格式
Print the number of different paths from (2,1) to (2,m) , taken modulo 109+7 . If it is impossible to get from (2,1) to (2,m) , then the number of paths is 0 .
输入输出样例
输入#1
2 5 1 3 4 2 2 3
输出#1
2