解題區/解題區 - UVa

UVa 804 - Petri Net Simulation

contents

  1. 1. Problem
  2. 2. Sample Input
  3. 3. Sample Output
  4. 4. Solution

Problem

上網搜尋 Petri Net ，得到是一個輸入輸出端的操作，當輸入端都至少一個時，將會進行觸發，每一次觸發會將輸入端都少一個元素，而輸出端會多一個元素。

現在模擬轉換 n 次，每一次轉換只能觸發一條，保證最終停留的結果只有一種，而當轉換失敗時，則宣告死亡。

Sample Input

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1 0
2
-1 2 0
-2 1 0
100
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3 0 0
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-1 2 0
-2 -2 3 0
-3 1 0
100
3
1 0 0
3
-1 2 3 0
-2 1 0
-3 1 0
1
0

Sample Output

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Case 1: still live after 100 transitions
Places with tokens: 1 (1)
Case 2: dead after 9 transitions
Places with tokens: 2 (1)
Case 3: still live after 1 transitions
Places with tokens: 2 (1) 3 (1)

Solution

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#include <stdio.h>
#include <map>
#include <queue>
#include <vector>
#include <sstream>
#include <iostream>
#include <algorithm>
using namespace std;
#define MAXN 1024
#define MAXM 1024
int N, P[MAXN], M, K;
vector<int> INPUT[MAXM], OUTPUT[MAXM];
void remove(int tid) {
    for (int i = 0; i < INPUT[tid].size(); i++) {
        P[INPUT[tid][i]]--;
    }
}
void resume(int tid) {
    for (int i = 0; i < INPUT[tid].size(); i++) {
        P[INPUT[tid][i]]++;
    }
}
int trigger(int tid) {
    int ok = 1;
    remove(tid);
    for (int i = 0; i < INPUT[tid].size(); i++)
        ok &= P[INPUT[tid][i]] >= 0;
    resume(tid);
    return ok;
}
void action(int tid) {
    remove(tid);
    for (int i = 0; i < OUTPUT[tid].size(); i++)
        P[OUTPUT[tid][i]]++;
}
void simulate() {
    for (int i = 0; i < K; i++) {
        int update = 0;
        for (int j = 0; j < M; j++) {
            if (trigger(j)) {
                update = 1;
                action(j);
                break;
            }
        }
        if (!update) {
            printf("dead after %d transitions\n", i);
            return;
        }
    }
    printf("still live after %d transitions\n", K);
}
int main() {
    int cases = 0;
    while (scanf("%d", &N) == 1 && N) {
        for (int i = 1; i <= N; i++)
            scanf("%d", &P[i]);
        scanf("%d", &M);
        for (int i = 0; i < M; i++) {
            int x;
            INPUT[i].clear(), OUTPUT[i].clear();
            while (scanf("%d", &x) == 1 && x) {
                if (x < 0)
                    INPUT[i].push_back(-x);
                if (x > 0)
                    OUTPUT[i].push_back(x);
            }
        }
        scanf("%d", &K);
        printf("Case %d: ", ++cases);
        simulate();
        printf("Places with tokens:");
        for (int i = 1; i <= N; i++) {
            if (P[i])
                printf(" %d (%d)", i, P[i]);
        }
        puts("\n");
    }
    return 0;
}
/*
 2
 1 0
 2
 -1 2 0
 -2 1 0
 100
 3
 3 0 0
 3
 -1 2 0
 -2 -2 3 0
 -3 1 0
 100
 3
 1 0 0
 3
 -1 2 3 0
 -2 1 0
 -3 1 0
 1
 0
 */