XidianOJ 1213 小V的滑板鞋

题目描述

输入

输出

摘自题解。。orz我还是太菜了

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
#define m first
#define w second
const int SIZE=1e5+7;

int c[SIZE];
struct shoe{
  int w,m;
} p[SIZE];
inline int lowbit(int x) {
  return x&-x;
}
void update(int x) {
  for(;x<SIZE;x+=lowbit(x))
    ++c[x];
}
int query(int x) {
  int res=0;
  for(;x>0;x-=lowbit(x)) res+=c[x];
  return res;
}
bool cmp(shoe s1,shoe s2){
  return (s1.m < s2.m);
}
int main(){
  freopen("test.in","r",stdin);
  int n,M,W;
  while((scanf("%d%d%d",&n,&M,&W)!= EOF))
  {
    for(int i=0;i<n;++i) scanf("%d",&p[i].m);
    for(int i=0;i<n;++i) scanf("%d",&p[i].w);
    sort(p,p+n,cmp);
    int l=0,r=n-1;
    LL ans=0;
    memset(c,0,sizeof(c));
    for(;r>=0;r--) {
      for(;l<n&&p[l].m+p[r].m<=M;++l)
        update(p[l].w);
      if(W-p[r].w>0) ans+=query(W-p[r].w);
    }
    for(int i=0;i<n;++i)
      if(p[i].m*2<=M&&p[i].w*2<=W)
        ans--;
    ans/=2;
    printf("%lld
",ans);
  }
  return 0;
}