对边权进行排序。令dp[i]表示以i为结束点的最大上升长度。那么，我们每一次加入一条边，dp[to]=dp[from]+1。其中需要注意，边权相等的时候，需要特殊考虑。
#include<iostream>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<cstdlib>
#include<climits>
#include<stack>
#include<vector>
#include<queue>
#include<set>
#include<bitset>
#include<map>
//#include<regex>
#include<cstdio>
#pragma GCC optimize(2)
#define up(i,a,b) for(int i=a;i<b;i++)
#define dw(i,a,b) for(int i=a;i>b;i--)
#define upd(i,a,b) for(int i=a;i<=b;i++)
#define dwd(i,a,b) for(int i=a;i>=b;i--)
//#define local
typedef long long ll;
typedef unsigned long long ull;
const double esp = 1e-6;
const double pi = acos(-1.0);
const int INF = 0x3f3f3f3f;
const int inf = 1e9;
using namespace std;
ll read()
{
char ch = getchar(); ll x = 0, f = 1;
while (ch<'0' || ch>'9') { if (ch == '-')f = -1; ch = getchar(); }
while (ch >= '0' && ch <= '9') { x = x * 10 + ch - '0'; ch = getchar(); }
return x * f;
}
typedef pair<int, int> pir;
#define lson l,mid,root<<1
#define rson mid+1,r,root<<1|1
#define lrt root<<1
#define rrt root<<1|1
const int N = 3e5 + 10;
struct eg {
int u, v, wi;
bool operator<(const eg temp)const {
return wi < temp.wi;
}
}edge[N];
int dp[N][2];
int n, m;
stack<eg>st;
int main()
{
n = read(), m = read();
int u, v, wi;
upd(i, 1, m)
{
u = read(), v = read(), wi = read();
edge[i].u = u; edge[i].v = v; edge[i].wi = wi;
}
sort(edge + 1, edge + 1 + m);
for (int i = 1; i <= m;)
{
st.push(edge[i]);
u = edge[i].u, v = edge[i].v, wi = edge[i].wi;
dp[v][1] = dp[u][0] + 1;
int j;
for ( j= i+1;j<=m &&edge[j-1].wi==edge[j].wi;j++)
{
st.push(edge[j]);
u = edge[j].u, v = edge[j].v, wi = edge[j].wi;
dp[v][1] = max(dp[v][1], dp[u][0] + 1);
}
i = j;
while (!st.empty())
{
eg top = st.top();
v = top.v;
dp[v][0] = max(dp[v][1], dp[v][0]);
dp[v][1] = 0;
st.pop();
}
}
int ans = 0;
upd(i, 1, n)
{
ans = max(ans, dp[i][0]);
}
cout << ans << endl;
return 0;
}原文：https://www.cnblogs.com/LORDXX/p/12523366.html