ZOJ 1508 差分约束

差分约数 找最短路 以终点为原点

相邻最多加1 将每条边 u v w 构造为 v 到 u-1 权值为-w

SPFA

#include <set>
#include <cmath>
#include <queue>
#include <stack>
#include <string>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

typedef  long long LL;
const double PI = acos(-1.0);

template <class T> inline  T MAX(T a, T b){if (a > b) return a;return b;}
template <class T> inline  T MIN(T a, T b){if (a < b) return a;return b;}

const int N = 111;
const int M = 11111;
const LL MOD = 1000000007LL;
const int dir[4][2] = {1, 0, -1, 0, 0, -1, 0, 1};
const int INF = 0x3f3f3f3f;


struct node
{
	int v, next, w;
}edge[222222];

int mx, mn, head[55555], cnt;
int dist[55555];
int inq[55555];


inline void addnode(int u, int v, int w)
{
	edge[cnt].v = v; edge[cnt].w = w;
	edge[cnt].next = head[u]; head[u] = cnt++;
}

void spfa()
{
	fill(dist, dist + mx + 1, INF);
	fill(inq, inq + mx + 1, 0);
	queue < int > q;
	q.push(mx);
	inq[mx] = 1; dist[mx] = 0;
	int i, j, k, u, v, w;
	while (!q.empty())
	{
		u = q.front(); q.pop(); inq[u]--;
//		getchar();
//		printf("%d\n", u);
//		for (i = 0; i <= 12; ++i) printf("%d ", dist[i]);
//		printf("\n");
		for (i = head[u]; ~i; i = edge[i].next)
		{
			v = edge[i].v; w = edge[i].w;
			if (dist[u] + w < dist[v])
			{
				dist[v] = dist[u] + w;
				if (!inq[v]) {inq[v]++; q.push(v);}
			}
		}
	}
}

int main()
{
	int m;
	while (scanf("%d", &m) != EOF)
	{
		memset(head, -1, sizeof(head));
		cnt = 0;
		int i, j, k, u, v, w;
		mn = INF; mx = -1;
		for (i = 0; i < m; ++i)
		{
			scanf("%d%d%d", &u, &v, &w);
			addnode(v, u - 1, -w);
			mn = MIN(mn, u);
			mx = MAX(mx, v);
		}
		for (i = 0; i < mx; ++i)
		{
			addnode(i, i + 1, 1);
			addnode(i + 1, i, 0);
		}
		spfa();
		printf("%d\n", dist[mx] - dist[mn - 1]);
	}
	return 0;
}