POJ - 2104(平方分割

又是二分边界处理出了问题，刚开始r初始值设置为n-1，但这样会导致l不可能取到n-1,所以r应该设为n,话说这题我居然跑了10s多，也算是破了个人记录了,orz

Accepted

1860

10829

G++

1249

2015-05-08 00:38:41

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<queue>
#include<utility>
#include<vector>
#include<cstring>
#include<cmath>
#define INF 0x3fffffff
#define pb push_back
#define pn(x) cerr<<x<<endl

using namespace std;
typedef long long ll;
const int maxv=100005;
const int B=1000;

int n,m;
int A[maxv];
int num[maxv];
vector<int> bucket[maxv/B];
ll calc(int l,int r,int m){///计算比m小的个数
    ll ans=0;
    if(l/B==r/B){
        for(int i=l;i<=r;i++){
            if(A[i]<m) ans++;
        }
        return ans;
    }
    int lb=(l+B)/B,rb=r/B;
    for(int i=l;i<lb*B;i++)
        if(A[i]<m) ans++;
    for(int i=rb*B;i<=r;i++)
        if(A[i]<m) ans++;
    for(int i=lb;i<rb;i++){
        ans+=lower_bound(bucket[i].begin(),bucket[i].end(),m)-bucket[i].begin();
    }
    return ans;
}
int main(){
    freopen("in.txt","r",stdin);
    //freopen("out.txt","w",stdout);
    scanf("%d%d",&n,&m);
    for(int i=0;i<n;i++){
        scanf("%d",&A[i]);
        num[i]=A[i];
        bucket[i/B].pb(A[i]);
    }
    for(int i=0;i<=(n-1)/B;i++) sort(bucket[i].begin(),bucket[i].end());
    sort(num,num+n);
    num[n]=INF;
    while(m--){
        ll i,j,k;
        scanf("%I64d%I64d%I64d",&i,&j,&k);
            ll l=0,r=n;
            while(r-l>1){
                ll mid=(r+l)/2;
                if(calc(i-1,j-1,num[mid])<k) l=mid;
                else r=mid;
            }
            printf("%d\n",num[l]);
    }
    return 0;
}