思路:
巧妙的线段树
想方法将网络流往数据结构方向转化
//By SiriusRen #include <bits/stdc++.h> using namespace std; typedef long long ll; const int N=200050; int n,m,q,X[N],y[N],tmp=1,xx,yy; ll tree[N<<2],lazy[N<<2],x[N]; struct Node{int from,to,wei;}node[N]; bool operator<(Node a,Node b){return a.from<b.from;} void insert(int l,int r,int pos,int L,int R,ll wei){ if(l>=L&&r<=R){tree[pos]+=wei;lazy[pos]+=wei;return;} int mid=(l+r)>>1,lson=pos<<1,rson=pos<<1|1; if(mid<L)insert(mid+1,r,rson,L,R,wei); else if(mid>=R)insert(l,mid,lson,L,R,wei); else insert(l,mid,lson,L,R,wei),insert(mid+1,r,rson,L,R,wei); tree[pos]=min(tree[lson],tree[rson])+lazy[pos]; } int main(){ scanf("%d%d%d",&n,&m,&q); for(int i=2;i<=n;i++)scanf("%lld%d",&x[i-1],&y[i]); for(int i=1;i<=m;i++)scanf("%d%d%d",&node[i].from,&node[i].to,&node[i].wei); for(int i=2;i<=n;i++)insert(1,n,1,i,i,y[i]); sort(node+1,node+1+m); for(int i=1;i<=n;i++){ for(;tmp<=m&&node[tmp].from<=i;tmp++) insert(1,n,1,1,node[tmp].to,node[tmp].wei); X[i]=x[i],x[i]+=tree[1]; }memset(tree,0,sizeof(tree)),memset(lazy,0,sizeof(lazy)); for(int i=1;i<=n;i++)insert(1,n,1,i,i,x[i]); printf("%lld\n",tree[1]); while(q--){ scanf("%d%d",&xx,&yy); insert(1,n,1,xx,xx,yy-X[xx]),X[xx]=yy; printf("%lld\n",tree[1]); } }