P1314 [NOIP2011 提高组] 聪明的质监员

最大值最小-》二分

#include<cstdio>
#include<iostream>
#include<algorithm>
//#include<queue>
//#include<vector>
#include<bits/stdc++.h>
#define ll long long
#define ddd printf("-----------------------\n");
using namespace std;
const int maxn=2e5+10 ;

struct node {
    ll v,w;
}a[maxn];

ll s,pre_v[maxn],pre_w[maxn],sum,ans=0x3f3f3f3f3f3f3f3f,rgt,lft=0x3f3f3f3f3f3f3f3f;
int n,m,l[maxn],r[maxn];

ll check(ll mid)
{
    memset(pre_v,0,sizeof(pre_v));
    memset(pre_w,0,sizeof(pre_w));
    sum=0;
    for(int i=1;i<=n;i++){
        if(a[i].w>=mid)
        {
            pre_w[i]=pre_w[i-1]+1;
            pre_v[i]=pre_v[i-1]+a[i].v;
        }
        else{
            pre_w[i]=pre_w[i-1];
            pre_v[i]=pre_v[i-1];
        }
    }
    for(int i=1;i<=m;i++)
        sum+=(pre_v[r[i]]-pre_v[l[i]-1])*(pre_w[r[i]]-pre_w[l[i]-1]);
    
    ans=min(ans,abs(s-sum));
    return sum>=s;
}
int main()
{
    ios::sync_with_stdio(false);
    cin>>n>>m>>s;
    for(int i=1;i<=n;i++){
        cin>>a[i].w>>a[i].v;
        rgt=max(a[i].w,rgt);
        lft=min(a[i].w,lft);
    }
    rgt+=2,lft-=1;
    for(int i=1;i<=m;i++){
        cin>>l[i]>>r[i];
    }
    while(lft<=rgt)//
    {
        ll mid=lft+rgt>>1;
        if(check(mid)) lft=mid+1;
        else rgt=mid-1;
    }
    
    cout<<ans<<'\n';
    
    return 0;
}