我知道这题 SPFA 会被卡，但是为什么会有 WA 的点，想知道哪错了。思路是差分约束跑最短路。

#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
bool START_MEMORY;

const int N = 1e5 + 5;
const ll inf = 1e18;

int n, m;
vector <pair <int, ll> > G[N];

queue <int> q;
ll dis[N];
int cnt[N];
bool vis[N], flag = true;
void spfa(){
    for(int i = 1; i <= n; i++) dis[i] = inf;
    q.push(0);
    vis[0] = true;
    cnt[0] = 1;
    while(!q.empty()){
        int u = q.front();
        q.pop();
        vis[u] = false;
        for(auto [v, w] : G[u]){
            if(dis[v] > dis[u] + w){
                dis[v] = dis[u] + w;
                if(!vis[v]){
                    q.push(v);
                    vis[v] = true;
                    if(++cnt[v] > n + 1){
                        flag = false;
                        return;
                    }
                }
            }
        }
    }
}

void Solve(){
    cin >> n >> m;
    int op, a, b;
    for(int i = 1; i <= m; i++){
        cin >> op >> a >> b;
        if(op == 1){ // a = b -> (a <= b + 0 and b <= a + 0)
            G[b].push_back(make_pair(a, 0));
            G[a].push_back(make_pair(b, 0));
        }else if(op == 2){ // a < b -> a <= b + (-1)
            G[b].push_back(make_pair(a, -1));
        }else if(op == 3){ // a >= b -> b <= a + 0
            G[a].push_back(make_pair(b, 0));
        }else if(op == 4){ // a > b -> b <= a + (-1)
            G[a].push_back(make_pair(b, -1));
        }else{ // a <= b -> a <= b + 0
            G[b].push_back(make_pair(a, 0));
        }
    }
    for(int i = 1; i <= n; i++) G[0].push_back(make_pair(i, 0));

    spfa();

    if(!flag) cout << -1 << "\n";
    else{
        ll ans = 0, mn = inf;
        for(int i = 1; i <= n; i++) mn = min(mn, dis[i]);
        mn = -mn + 1;
        mn = max(mn, 0ll);
        for(int i = 1; i <= n; i++) ans += dis[i] + mn;
        cout << ans << "\n";
    }
}

bool END_MEMORY;
int main(){
    ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    int T = 1;
    // cin >> T;
    while(T--) Solve();

    cerr << "Time: " << 1000 * clock() / CLOCKS_PER_SEC << " ms\n";
    cerr << "Memory: " << fixed << setprecision(3) << double(&END_MEMORY - &START_MEMORY) / 1024 << " KB\n";
    return 0;
}