题目

链接：https://ac.nowcoder.com/acm/contest/11257/I
来源：牛客网

时间限制：C/C++ 1秒，其他语言2秒
空间限制：C/C++ 262144K，其他语言524288K
Special Judge, 64bit IO Format: %lld

题目描述

There is a ring of numbers consisting of 111 to nnn sequentially. For every number iii (1≤i≤n−1)(1 \leq i \leq n - 1)(1≤i≤n−1), iii and i+1i+1i+1 are adjacent to each other. Particularly, nnn and 111 are adjacent. We use [l,r][l,r][l,r] to describe an interval on the ring. Formally, if l≤rl \leq rl≤r, then the interval [l,r][l,r][l,r] is equivalent to the set {l,l+1,…,r−1,r}{ l, l + 1, \ldots, r - 1, r }{l,l+1,…,r−1,r}. Otherwise, the interval [l,r][l,r][l,r] is equivalent to {l,l+1,…,n,1,…,r−1,r}{l,l+1,\ldots,n,1,\ldots,r-1,r}{l,l+1,…,n,1,…,r−1,r}.

Yukikaze has mmm non-intersecting intervals. She wants you to construct a set of intervals such that the intersection of them is the union of the mmm intervals that Yukikaze has. The intersection of the intervals is the set of integers that the intervals have in common.

输入描述:

The first line of the input contains a single integer T (1≤T≤1000)T\ (1 \leq T \leq 1000)T (1≤T≤1000), denoting the number of test cases.The first line of each test case contains two integers n (3≤n≤1000)n\ (3 \leq n \leq 1000)n (3≤n≤1000) and m (1≤m≤n)m\ (1 \leq m \leq n)m (1≤m≤n), denoting that the ring consists of numbers from 111 to nnn.Each of the next mmm lines contains two integers l,r (1≤l,r≤n)l,r\ (1 \leq l, r \leq n)l,r (1≤l,r≤n), denoting an interval Yukikaze has. It's guaranteed that the mmm intervals won't intersect with each other.

输出描述:

For each test case, if the answer doesn't exist, output −1-1−1 in a line. Otherwise, output an integer kkk indicating the number of intervals you construct in a line. Then output the kkk intervals in kkk lines. The number of intervals you used should never be less than one or greater than 200020002000. If there are multiple solutions, print any. Don't print any extra spaces at the end of each line.

示例1

输入

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2021牛客多校6 I Intervals on the Ring

题目

题目描述

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输出描述:

输入

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