【HDOJ】4109 Instrction Arrangement

差分约束。

/* 4109 */
#include <iostream>
#include <queue>
#include <vector>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <climits>
using namespace std;

#define MAXV 1005
#define MAXE 41005
#define INF  0x3f

typedef struct {
    int v, w, next;
} Edge_t;

Edge_t E[MAXE];
int head[MAXV], L;
int dis[MAXV];
bool visit[MAXV];
int n, m;

void init() {
    for (int i=0; i<=n; ++i)
        dis[i] = INT_MIN;
    memset(head, -1, sizeof(int)*(n+1));
    memset(visit, false, sizeof(bool)*(n+1));
    L = 0;
}

void addEdge(int u, int v, int w) {
    E[L].v = v;
    E[L].w = w;
    E[L].next = head[u];
    head[u] = L++;
}

void spfa() {
    int i, j, k;
    int u, v, w;
    queue<int> Q;

    visit[n] = true;
    dis[n] = 0;
    Q.push(n);

    while (!Q.empty()) {
        u = Q.front();
        Q.pop();
        visit[u] = false;
        for (i=head[u]; i!=-1; i=E[i].next) {
            v = E[i].v;
            w = E[i].w;
            if (dis[v] < dis[u]+w) {
                dis[v] = dis[u] + w;
                if (!visit[v]) {
                    visit[v] = true;
                    Q.push(v);
                }
            }
        }
    }
}

int main() {
    int i, j, k;

    #ifndef ONLINE_JUDGE
        freopen("data.in", "r", stdin);
        freopen("data.out", "w", stdout);
    #endif

    while (scanf("%d %d",&n,&m) != EOF) {
        init();
        while (m--) {
            scanf("%d%d%d", &i, &j, &k);
            addEdge(j, i, k);
        }
        for (i=0; i<n; ++i)
            addEdge(n, i, 0);
        spfa();
        k = INT_MIN;
        for (i=0; i<=n; ++i)
            k = max(k, dis[i]);
        printf("%d
", k+1);
    }

    return 0;
}