Zoj 2770 burn the linked camp difference constraint + spfa

The first positive difference Constraint

There are n vertices in a column. First, tell you the maximum value of each vertex (at least obviously greater than 0), and then tell you the M segment I, J, K, the sum of the values from point I to Point J has at least K and asks you at least the sum.

It should be noted that do not forget to build the edge for all the relationships that you have provided. At first, the condition greater than 0 is missing and adjusted for half a day O (else □else) O

The inequality is in the form of a-B <= c =

 1 #include <cstdio> 2 #include <cstring> 3 #include <cmath> 4 #include <algorithm> 5 #include <climits> 6 #include <string> 7 #include <iostream> 8 #include <map> 9 #include <cstdlib>10 #include <list>11 #include <set>12 #include <queue>13 #include <stack>14 15 using namespace std;16 17 typedef long long LL;18 const int maxn = 1000 + 5;19 const int maxm = 50000 + 5;20 const LL INF = LONG_LONG_MAX / 4;21 int v[maxm],w[maxm],first[maxn],nxt[maxm];22 int n,m,C,cnt[maxn],ecnt;23 LL d[maxn];24 bool inq[maxn];25 26 void solve() {27     bool bad = false;28     queue<int> q;29     q.push(n);30     for(int i = 0;i <= n;i++) {31         inq[i] = false;32         d[i] = INF;33         cnt[i] = 0;34     }35     d[n] = 0;36     inq[n] = true;37     cnt[n] = 1;38     while(!q.empty() && !bad) {39         int x = q.front(); q.pop();40         inq[x] = false;41         for(int i = first[x];i != -1;i = nxt[i]) {42             if(d[v[i]] > d[x] + w[i]) {43                 d[v[i]] = d[x] + w[i];44                 if(!inq[v[i]]) {45                     q.push(v[i]);46                     cnt[v[i]]++;47                     inq[v[i]] = true;48                     if(cnt[v[i]] > n + 1) {49                         bad = true; break;50                     }51                 }52             }53         }54     }55     if(bad) puts("Bad Estimations");56     else printf("%lld\n",-d[0]);57 }58 59 void adde(int _u,int _v,int _w) {60     v[ecnt] = _v; w[ecnt] = _w;61     nxt[ecnt] = first[_u];62     first[_u] = ecnt;63     ecnt++;64 }65 66 int main() {67     while(~scanf("%d%d",&n,&m)) {68         ecnt = 0;69         memset(first,-1,sizeof(first));70         memset(nxt,-1,sizeof(nxt));71         for(int i = 1;i <= n;i++) {72            scanf("%d",&C);73            adde(i - 1,i,C);74            adde(i,i - 1,0);75         }76         for(int i = 1;i <= m;i++) {77             int a,b,c; scanf("%d%d%d",&a,&b,&c);78             adde(b,a - 1,-c);79         }80         solve();81     }82     return 0;83 }