codeforces 1367B - Even Array
2412 ワード
B. Even Array time limit per test2 seconds memory limit per test256 megabytes inputstandard input outputstandard output You are given an array a[0…n−1] of length n which consists of non-negative integers. Note that array indices start from zero.
An array is called good if the parity of each index matches the parity of the element at that index. More formally, an array is good if for all i (0≤i≤n−1) the equality imod2=a[i]mod2 holds, where xmod2 is the remainder of dividing x by 2.
For example, the arrays [0,5,2,1] and [0,17,0,3] are good, and the array [2,4,6,7] is bad, because for i=1, the parities of i and a[i] are different: imod2=1mod2=1, but a[i]mod2=4mod2=0.
In one move, you can take any two elements of the array and swap them (these elements are not necessarily adjacent).
Find the minimum number of moves in which you can make the array a good, or say that this is not possible.
Input The first line contains a single integer t (1≤t≤1000) — the number of test cases in the test. Then t test cases follow.
Each test case starts with a line containing an integer n (1≤n≤40) — the length of the array a.
The next line contains n integers a0,a1,…,an−1 (0≤ai≤1000) — the initial array.
Output For each test case, output a single integer — the minimum number of moves to make the given array a good, or -1 if this is not possible.
Example inputCopy 4 4 3 2 7 6 3 3 2 6 1 7 7 4 9 2 1 18 3 0 outputCopy 2 1 -1 0 Note In the first test case, in the first move, you can swap the elements with indices 0 and 1, and in the second move, you can swap the elements with indices 2 and 3.
In the second test case, in the first move, you need to swap the elements with indices 0 and 1.
In the third test case, you cannot make the array good.
リンク:https://codeforces.ml/problemset/problem/1367/B题意:1つの配列の中のすべてのi%2がa[i]%2と等しいならgood、出力交换の回数、等しくなければ、交换を通じて配列がgoodにならないかどうかを见て出力-1の考え方:できる回数を统计するだけで、统计するだけでいい.配列に偶数奇数偶数奇数が必要であることが判明したので...a[i]が対応する偶数または奇数であるか否かを判断し、そうでなければ統計し、最後に統計した奇数が等しいか否かを判断するacコードは以下の通りである.
An array is called good if the parity of each index matches the parity of the element at that index. More formally, an array is good if for all i (0≤i≤n−1) the equality imod2=a[i]mod2 holds, where xmod2 is the remainder of dividing x by 2.
For example, the arrays [0,5,2,1] and [0,17,0,3] are good, and the array [2,4,6,7] is bad, because for i=1, the parities of i and a[i] are different: imod2=1mod2=1, but a[i]mod2=4mod2=0.
In one move, you can take any two elements of the array and swap them (these elements are not necessarily adjacent).
Find the minimum number of moves in which you can make the array a good, or say that this is not possible.
Input The first line contains a single integer t (1≤t≤1000) — the number of test cases in the test. Then t test cases follow.
Each test case starts with a line containing an integer n (1≤n≤40) — the length of the array a.
The next line contains n integers a0,a1,…,an−1 (0≤ai≤1000) — the initial array.
Output For each test case, output a single integer — the minimum number of moves to make the given array a good, or -1 if this is not possible.
Example inputCopy 4 4 3 2 7 6 3 3 2 6 1 7 7 4 9 2 1 18 3 0 outputCopy 2 1 -1 0 Note In the first test case, in the first move, you can swap the elements with indices 0 and 1, and in the second move, you can swap the elements with indices 2 and 3.
In the second test case, in the first move, you need to swap the elements with indices 0 and 1.
In the third test case, you cannot make the array good.
リンク:https://codeforces.ml/problemset/problem/1367/B题意:1つの配列の中のすべてのi%2がa[i]%2と等しいならgood、出力交换の回数、等しくなければ、交换を通じて配列がgoodにならないかどうかを见て出力-1の考え方:できる回数を统计するだけで、统计するだけでいい.配列に偶数奇数偶数奇数が必要であることが判明したので...a[i]が対応する偶数または奇数であるか否かを判断し、そうでなければ統計し、最後に統計した奇数が等しいか否かを判断するacコードは以下の通りである.
#include
#include
using namespace std;
int main()
{
int t,a[1002];
cin>>t;
while(t--)
{
int n,cou1=0,cou2=0;
cin>>n;
for(int i=0;i>a[i];
}
for(int i=0;i