HDU 5166 Missing number 简单数论

Missing number

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)

【Problem Description】

There is a permutation without two numbers in it, and now you know what numbers the permutation has. Please find the two numbers it lose.

 

【Input】

There is a number T shows there are T test cases below. (T≤10)
For each test case , the first line contains a integers n , which means the number of numbers the permutation has. In following a line , there are n distinct postive integers.(1≤n≤1,000)

 

【Output】

For each case output two numbers , small number first.

 

【Sample Input】

2 
3 
3 4 5 
1 
1

 

【Sample Output】

1 2 
2 3

【题意】

找出一个数列中缺的两个数。

 

【分析】

本来没啥好说的，记录完了之后O(n)扫描一遍即可，启发就是一种简单的O(1)的算法也要多多注意下。

Sum(n)    =n*(n+1)/2
Sum(n^2)  =n*(n+1)*(2n+1)/6