Title:
Here is given 2*n cards, the value of each card is different, two people A and B arbitrarily choose 1 card from them, and then discard these 2 cards. one point
Now I ask you, what is the expectation of A to get the score
answer:
First we have 2*n cards, the optimal score is n->A draw the largest n cards
The worst score is 0->A draw the smallest n sheets
So for A, the expected score that A can get is (n+0) / 2
In fact, the expectation here can be regarded as the average. The probability is equal.
In summary, the code is well written:
#include<iostream> #include<cstdio> #include<cstring> #include<algorithm> using namespace std; const int maxn = 10000100; bool force[maxn]; intmain() { int caset,cas=0;scanf("%d",&caset); while(caset--) { int n;scanf("%d",&n); for(int i=0,x;i<2*n;i++) scanf("%d",&x); printf("Case %d: %.2f\n",++cas,1.0*n/2); } return 0; }