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;}