[Link] https://codeforces.com/contest/1637/problem/C
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
import java.util.*;
import java.io.*;
public class Main {
static BufferedReader br;
static StringBuilder sb = new StringBuilder();
public static void main(String[] args) throws IOException {
br = new BufferedReader(new InputStreamReader(System.in));
StringBuilder sb = new StringBuilder();
int test = toi(br.readLine());
int[] arr;
for(int iter = 0; iter < test; iter++) {
int n = toi(br.readLine());
arr = getArr();
if(n == 3) { // l (odd) r
sb.append((arr[1] & 1) == 1 ? -1 : arr[1]/2).append("\n");;
} else { // l 1...1 r
boolean allOne = true;
int oddCnt = 0;
long sum = 0;
for(int i = 1; i < n-1; i++) {
if(arr[i] != 1) allOne = false;
if((arr[i] & 1) == 1) oddCnt++;
sum += arr[i];
}
if(allOne) sb.append(-1);
else sb.append((oddCnt + sum) / 2);
sb.append("\n");
}
}
print(sb);
}
static int toi(String s) { return Integer.parseInt(s); }
static String[] getLine() throws IOException { return br.readLine().split(" "); }
static int[] getArr() throws IOException { return Arrays.stream(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray(); }
static <T> void print(T s) { System.out.print(s); }
static <T> void println(T s) { System.out.println(s); }
}