zoj 2770 Burn the Linked Camp 差分约束

设x[i] 为第i个营的人数，s[i] = x[1] + x[2] + … + x[i], s[0] = 0

则对于题目

Ci 有： 0 <= s[i] – s[i-1] <= Ci

i, j, k有： s[j] – s[i-1] >= k

还有： s[i] >= 0 (1 <= i <= n) , 即 s[i] – s[0] >= 0

这题求最小值，以0为源点求最长路

#include<iostream>
#include <queue>
#include <cstdio>
#include <cstring>
using namespace std;

const int MAX = 20000;
const int INF = 1000000000;
const int N = 10000;

struct Node
{
int v;
int cost;
int next;
};

Node node[MAX];
int adj
;
int d
;
bool in_q
;
int cnt
;
int size;
int n, m;

void add_edge(int u, int v, int cost)
{
node[size].v = v;
node[size].cost = cost;
node[size].next = adj[u];
adj[u] = size++;
}

bool spfa()
{
queue<int> Q;

memset(in_q, false, sizeof(in_q));
memset(cnt, 0, sizeof(cnt));
for (int i = 0; i <= n; i++)
d[i+1] = -INF;

int u, v, w;
d[0] = 0;
Q.push(0);
in_q[0] = true;

while (!Q.empty())
{
u = Q.front();
Q.pop();
in_q[u] = false;

for (int i = adj[u]; i != -1; i = node[i].next)
{
v = node[i].v;
w = node[i].cost;

if (d[v] < d[u] + w)
{
d[v] = d[u] + w;
if (!in_q[v])
{
in_q[v] = true;
Q.push(v);
}

if (++cnt[v] > n) return false;
}
}
}

return true;
}

int main()
{
int u, v, w;

while (cin >> n >> m)
{
size = 0;
for (int i = 0; i <= n+1; i++)
adj[i] = -1;

int c;
for (int i = 1; i <= n; i++)
{
scanf("%d", &c);
add_edge(i-1, i, 0);
add_edge(i, i-1, -c);
}

for (int i = 1; i <= n; i++)
add_edge(0, i, 0);

for (int i = 0; i < m; i++)
{
scanf("%d%d%d", &u, &v, &w);
add_edge(u-1, v, w);
}

if (spfa())
{
printf("%d\n", d
);
}
else
printf("Bad Estimations\n");
}
return 0;
}