[POI2005]AUT-The Bus 树状数组维护最大前缀和

#include<cstdio>
#include<algorithm>
using namespace std;
const int N=100000+3;
int x[N], y[N], Y[N], A[N], nums[N];
int C[N];
int cmp(int i,int j){
    if(x[i]==x[j])return y[i]<y[j];
    return x[i]<x[j];
}
int lowbit(int t){return t&(-t);}
void update(int t,int delta)
{
    while(t<N) C[t]=max(C[t],delta),  t+=lowbit(t);
}
int query(int t){
    int tmp=-1;
    while(t>0)tmp=max(tmp,C[t]), t-=lowbit(t);
    return tmp;
}
int main()
{
    //freopen("in.txt","r",stdin);
    int n,m,k,ans=0;
    scanf("%d%d%d",&n,&m,&k);
    for(int i=1;i<=k;++i)scanf("%d%d%d",&y[i],&x[i],&nums[i]), Y[i]=y[i];
    for(int i=1;i<=k;++i)A[i]=i;
    sort(A+1,A+1+k,cmp);
         sort(Y+1,Y+1+k);
    for(int i=1;i<=k;++i)
    {
        int cur=A[i];
        y[cur]=lower_bound(Y+1,Y+1+k, y[cur])-Y;
        int h=query(y[cur])+nums[cur];
        ans=max(ans,h);
        update(y[cur], h);
    }
    printf("%d",ans);
    return 0;
}