Pathwalks CodeForces - 960F(主席树 || 树状数组)

#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e6+10, INF = 0x7fffffff;
int n, m, maxx = -INF;
map<int, int> edge[maxn];
int lowbit(int x)
{
    return x & -x;
}
int qp(int u, int w)
{
    int ret = 0;
    for(int i=w; i>0; i-=lowbit(i))
        ret = max(ret, edge[u][i]);
    return ret;
}

int build(int u, int w, int ans)
{
    while(w)
    {
        edge[u][w] = max(edge[u][w], ans);
        w += lowbit(w);
    }

}

int main()
{
    int u, v, w;
    cin >> n >> m;
    for(int i=0; i<m; i++)
    {
        cin >> u >> v >> w;
        maxx = max(maxx, w);
        build(v, +1, qp(u, w)+1);
    }
    int max_ret = -INF;
    for(int i=1; i<=n; i++)
        max_ret = max(max_ret, qp(i, 100001));
    cout << max_ret << endl;


    return 0;
}