题目描述:
There are two sisters Alice and Betty. You have n candies. You want to distribute these n candies between two sisters in such a way that:
Alice will get a (a>0) candies;
Betty will get b (b>0) candies;
each sister will get some integer number of candies;
Alice will get a greater amount of candies than Betty (i.e. a>b);
all the candies will be given to one of two sisters (i.e. a+b=n).
Your task is to calculate the number of ways to distribute exactly n candies between sisters in a way described above. Candies are indistinguishable.
Formally, find the number of ways to represent n as the sum of n=a+b, where a and b are positive integers and a>b.
You have to answer t independent test cases.
输入描述:
The first line of the input contains one integer t (1≤t≤104) — the number of test cases. Then t test cases follow.
The only line of a test case contains one integer n (1≤n≤2⋅109) — the number of candies you have.
输出描述:
For each test case, print the answer — the number of ways to distribute exactly n candies between two sisters in a way described in the problem statement. If there is no way to satisfy all the conditions, print 0.
输入:
6
7
1
2
3
2000000000
763243547
输出:
3
0
0
1
999999999
381621773
题意:
一个数分解成a+b,几种分解法,a!=b
题解:
分奇偶讨论一下
代码:
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20#include<cstdio> #include<cstring> #include<algorithm> #include<iostream> using namespace std; int main(){ int t,n; scanf("%d",&t); while(t--){ scanf("%d",&n); int ans; if(n % 2 == 0){ ans = n / 2 - 1; } else ans = n / 2; printf("%dn",ans); } return 0; }
最后
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