题解——Codeforces Round #508 (Div. 2) T3 （贪心）

贪心的选取最优解

然后相减好

记得要开long long

#include <cstdio>
#include <algorithm>
#include <cstring>
#include <set>
#include <queue>
#define int long long
using namespace std;
int ansa=0,ansb=0,posa=1,posb=1,n,a[1000100],b[1000100];
bool cmp(int a,int b){
  if(a>b)
    return true;
  else
    return false;
}
signed main(){
  scanf("%I64d",&n);
  for(int i=1;i<=n;i++)
    scanf("%I64d",&a[i]);
  for(int i=1;i<=n;i++)
    scanf("%I64d",&b[i]);
  sort(a+1,a+n+1,cmp);
  sort(b+1,b+n+1,cmp);
  int whi=0;// 0 a 1 b
  while(posa<=n||posb<=n){
    if(whi==0){
      if(a[posa]>b[posb]&&posa<=n){
        ansa+=a[posa];
        posa++;
        whi=1-whi;
      }
      else if(a[posa]<=b[posb]&&posb<=n){
        posb++;
        whi=1-whi;
      }
      else if(posb<=n){
        posb++;
        whi=1-whi;
      }
      else if(posa<=n){
        ansa+=a[posa];
        posa++;
        whi=1-whi;
      }
    }
    else{
      if(b[posb]>a[posa]&&posb<=n){
        ansb+=b[posb];
        posb++;
        whi=1-whi;
      }
      else if(b[posb]<=a[posa]&&posa<=n){
        posa++;
        whi=1-whi;
      }
      else if(posa<=n){
        posa++;
        whi=1-whi;
      }
      else if(posb<=n){
        ansb+=b[posb];
        posb++;
        whi=1-whi;
      }
    }
  }
  printf("%I64d",ansa-ansb);
  return 0;
}