lg3431

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链接:lg3431

题解

nm很小的话可以O(nm)dp
离散化后转移方程f[i]=max(f[j])+val   (a[i].y>=a[j].y)
这里显然是个二位偏序,树状数组维护一下

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#include<bits/stdc++.h>
#define rep(i,x,y) for(register int i=x;i<=y;++i)
#define lowbit(x) x&(-x)
#define ll long long
using namespace std;
const int N=1e5+7;
struct node{
    int l,r;
    ll x;
}a[N];
int n,m,k,nx,ny;
ll c[N],f[N],ans=-1;
int X[N],Y[N];
map<int,int>hsh_x,hsh_y;
inline int cmp(node x,node y){return x.l==y.l?x.r<=y.r:x.l<y.l;}
void update(int x,ll k){
    for(int i=x;i<=ny;i+=lowbit(i))c[i]=max(c[i],k);
}
ll query(int x){
    ll res=-1;
    for(int i=x;i;i-=lowbit(i))res=max(c[i],res);
    return res;
}
int main(){
    scanf("%d%d%d",&n,&m,&k);
    rep(i,1,k){
        scanf("%d%d%lld",&a[i].l,&a[i].r,&a[i].x);
        X[i]=a[i].l;
        Y[i]=a[i].r;
    }
    sort(X+1,X+k+1);
    sort(Y+1,Y+k+1);
    rep(i,1,k){
        if(X[i]!=X[i-1])hsh_x[X[i]]=++nx;
        if(Y[i]!=Y[i-1])hsh_y[Y[i]]=++ny;
    }
    rep(i,1,k)a[i].l=hsh_x[a[i].l],a[i].r=hsh_y[a[i].r];
    sort(a+1,a+k+1,cmp);
    rep(i,1,k){
        f[i]=query(a[i].r)+a[i].x;
        update(a[i].r,f[i]);
    }
    rep(i,1,k)ans=max(ans,f[i]);
    printf("%lld\n",ans);
    return 0;
}