HDU 5700区间交(百度之星2B)

分析：

代码：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <set>
#include <map>
#include <queue>
#include <vector>
#include <string>

using namespace std;

typedef long long LL;
typedef vector <int>    VI;
typedef pair <int,int>  PII;
#define FOR(i,x,y)  for(int i = x;i < y;++ i)
#define IFOR(i,x,y) for(int i = x;i > y;-- i)
#define pb  push_back
#define mp  make_pair
#define fi  first
#define se  second
#define lrt rt<<1
#define rrt rt<<1|1
#define lson    rt<<1,l,mid
#define rson    rt<<1|1,mid+1,r

const int maxn = 100010;
int n,k,m;
LL a[maxn],sum[maxn];
VI  id[maxn];

struct Seg{
int l,r;
bool operator < (const Seg &rhs) const{
return l < rhs.l;
}
}seg[maxn];

struct Tree{
int l,r;
int cnt;
int maxx,minx;
}tree[maxn<<2];

void pushup(int rt){
tree[rt].maxx = max(tree[lrt].maxx,tree[rrt].maxx);
tree[rt].minx = min(tree[lrt].minx,tree[rrt].minx);
}

void pushdown(int rt){
if(tree[rt].l == tree[rt].r)    return ;
if(tree[rt].cnt){
tree[lrt].maxx += tree[rt].cnt;
tree[rrt].maxx += tree[rt].cnt;
tree[lrt].minx += tree[rt].cnt;
tree[rrt].minx += tree[rt].cnt;
tree[lrt].cnt += tree[rt].cnt;
tree[rrt].cnt += tree[rt].cnt;
tree[rt].cnt = 0;
}
}

void build(int rt,int l,int r){
tree[rt].l = l; tree[rt].r = r;
tree[rt].cnt = 0;   tree[rt].minx =tree[rt].maxx = 0;
if(l == r)  return;
int mid = (l+r)>>1;
build(lson);
build(rson);
}

void modify(int rt,int l,int r,int val){
if(tree[rt].l == l && tree[rt].r == r){
tree[rt].cnt += val;
tree[rt].maxx += val;
tree[rt].minx += val;
return;
}
pushdown(rt);
int mid = (tree[rt].l+tree[rt].r)>>1;
if(r <= mid)    modify(lrt,l,r,val);
else if(l > mid)    modify(rrt,l,r,val);
else    {modify(lson,val);modify(rson,val);}
pushup(rt);
}

int query(int rt){
pushdown(rt);
if(tree[rt].maxx < k)   return  -1;
if(tree[rt].minx >= k)  return  tree[rt].r;
if(tree[rrt].maxx >= k)  return  query(rrt);
return query(lrt);
}

void work(){
LL ans = 0;
build(1,1,n);
int x = 0;
FOR(i,1,n+1){
//if(i == 4)
//printf("hh\n");
while(x < m && seg[x].l <= i){
modify(1,i,seg[x].r,1);
x ++;
}
int r = query(1);
if(r >= i)  ans = max(ans,sum[r]-sum[i-1]);
}
printf("%I64d\n",ans);
}

int main(){
//freopen("test.in","r",stdin);
while(~scanf("%d%d%d",&n,&k,&m)){
sum[0] = 0;
FOR(i,1,n+1)    scanf("%I64d",&a[i]),sum[i] = sum[i-1]+a[i];
FOR(i,0,m)      scanf("%d%d",&seg[i].l,&seg[i].r);
sort(seg,seg+m);
work();
}
return 0;
}