CF621A - Wet Shark and Odd and Even

题目大意：给你n个数，每个数选或不选，加起来得到一个偶数，求最大偶数。

排序，偶数在前，奇数在后，奇偶分别递减。偶数直接加，奇数两个两个加，扫一遍即可。

#include<cstdio>#include<iostream>#include<cstring>#include<string>#include<algorithm>#include<cmath>using namespace std;struct aaa{long long x;bool friend operator<(aaa a,aaa b){if(a.x%2==b.x%2)return a.x>b.x;if(a.x%2==0)return 1;return 0;}}a[110000];int n;int main(){scanf("%d",&n);for(int i=1;i<=n;i++){int x;scanf("%d",&x);a[i].x=x;}sort(a+1,a+1+n);long long ans=0;for(int i=1;i<=n;i++){if(a[i].x%2==0){ans+=a[i].x;}else{if(i+1<=n){ans+=a[i].x+a[i+1].x;a[i].x=a[i+1].x=0;}}}cout<<ans<<endl;return 0;}