RaAlGhul的博客

敌兵布阵 Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 66927    Accepted Submission(s): 28200 Problem Description C国的死对头A国这段时间正在进行军事演

Color the ball Time Limit: 9000/3000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 14633    Accepted Submission(s): 7309 Problem Description N个气球排成一排，从

Frosh Week Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 2565    Accepted Submission(s): 851 Problem Description During Frosh Wee

See you~ Time Limit: 5000/3000 MS (Java/Others)    Memory Limit: 65535/32768 K (Java/Others) Total Submission(s): 4414    Accepted Submission(s): 1396 Problem Description Now I am leaving

Stars Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 7307    Accepted Submission(s): 2875 Problem Description Astronomers often ex

MooFest Time Limit : 2000/1000ms (Java/Other)   Memory Limit : 60000/30000K (Java/Other) Total Submission(s) : 32   Accepted Submission(s) : 16 Problem Description Every year, Farmer John'

Find the nondecreasing subsequences Time Limit: 10000/5000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 1791    Accepted Submission(s): 655 Problem Descr

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=5792 题意，给我们n个数的序列A，问我们能够找到多少四个不同位置a,b,c,d的数满足：a≠b≠c≠d,1≤aAd. 这题很明显可以用到容斥原理去处理，我们可以先找到所有的情况然后我们再去减去多余的部分即可，算总个数显然就是所有的上升序列个数*所有的下降序列的个数。仔细思考，我们多余的是哪