题解 | 灵异背包？

#include <iostream>
#include<vector>
#include<algorithm>
using namespace std;

int main() {
    int n;
    cin>>n;
    int a[100000];
    long long sum=0;
    vector<int> odds;

    for (int i = 0; i<n; i++) {
        cin>>a[i];
        sum+=a[i];//直接累加，最后总和是不是偶数
        if (a[i]%2==1) {
            odds.push_back(a[i]);
        }
    }

    if (sum%2==0) {
        cout<<sum<<endl;
    }
    else if (odds.empty()) {
        cout<<0<<endl;
    }
    else {
        sort(odds.begin(), odds.end());//移除里面最小的奇数。让总数为最大偶数
        cout << sum - odds[0] << endl;
    }

}

有点难，直接求总数再判断，用vector写更好看，也可以直接找最小奇数、直接判断有没有偶数：

#include <iostream>
#include <climits>
using namespace std;

int main() {
    int n, x, minOdd = INT_MAX;
    long long sum = 0;
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> x;
        sum += x;
        if (x % 2 == 1) minOdd = min(minOdd, x);
    }
    if (sum % 2 == 0) cout << sum << endl;
    else if (minOdd == INT_MAX) cout << 0 << endl;
    else cout << sum - minOdd << endl;
    return 0;
}