08-图9 关键活动

#include <stdio.h>#define MAXINT 0x7fffffff#define Max 101int Graph[Max][Max], Indegree[Max], Outdegree[Max], Earliest[Max], Latest[Max];int max(int a, int b){if (a > b)return a;elsereturn b;}int min(int a, int b){if (a < b)return a;elsereturn b;}int Earliest_Time(int N);void Latest_Time(int N, int res);int main(int argc, char const *argv[]){// freopen("test.txt", "r", stdin);int N, M;scanf("%d %d", &N, &M);for (int i = 1; i <= N; i++){for (int j = 0; j <= N; j++){Graph[i][j] = -1;}Indegree[i] = 0;Outdegree[i] = 0;Earliest[i] = 0;Latest[i] = MAXINT;}int s, e, c;for (int i = 0; i < M; i++){scanf("%d %d %d", &s, &e, &c);Graph[s][e] = c;Outdegree[s]++;Indegree[e]++;}int res = Earliest_Time(N);Latest_Time(N, res);if (res == -1)printf("0");else{printf("%d\n", res);for (int i = 1; i <= N; i++){if (Earliest[i] != Latest[i])continue;for (int j = N; j >= 1; j--){if (Graph[i][j] >= 0 && Earliest[j] == Latest[j] && (Latest[j] - Earliest[i] == Graph[i][j]))printf("%d->%d\n", i, j);}}}return 0;}int Earliest_Time(int N){int queue[N+1], front = 0, rear = 0;for (int i = 1; i <= N; i++){if (Indegree[i] == 0){queue[rear++] = i;Indegree[i]--;}}int cnt = 0, v;while (rear - front){v = queue[front++];cnt++;for (int i = 1; i <= N; i++){if (Graph[v][i] >= 0){Indegree[i]--;Earliest[i] = max(Earliest[i], Earliest[v] + Graph[v][i]);}if (Indegree[i] == 0){queue[rear++] = i;Indegree[i]--;}}}int res = 0;if (cnt != N)return -1;else {for (int i = 1; i <= N; i++){if (Outdegree[i] == 0)res = max(res, Earliest[i]);}return res;}}void Latest_Time(int N, int res){int queue[N+1], front = 0, rear = 0;for (int i = 1; i <= N; i++){if (Outdegree[i] == 0){queue[rear++] = i;Latest[i] = res;// Outdegree[i]--;}}int v;while (rear - front){v = queue[front++];for (int i = N; i >= 1; i--){if (Graph[i][v] >= 0){Outdegree[i]--;Latest[i] = min(Latest[i], Latest[v] - Graph[i][v]);if (Outdegree[i] == 0)queue[rear++] = i;}}}}