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  • 暗黑城堡---最小生成树?????

    这题哪里和最小生成树有关系???

    不明白呀!

    问有几条路径的题,一般都是乘法原理

    #include<iostream>
    #include<cstring>
    #include<queue>
    #include<vector>
    #include<algorithm>
    #define maxn 1010
    using namespace std;
    const long long INF = 2147483647;
    int dis[maxn];
    int vis[maxn];
    struct Node {
    	int p;
    	int len;
    	Node(int a, int b) :p(a), len(b) {}
    };
    int cnt[maxn];
    vector<Node>G[maxn];
    void insert(int be, int en, int len) {
    	G[be].push_back(Node(en, len));
    }
    int n, m;
    bool operator < (const Node a, const Node b) {
    	return a.len > b.len;
    }
    int dijstra() {
    	memset(dis, 0x3f3f3f3f,sizeof(dis));
    	priority_queue<Node>que;
    	que.push(Node(1,0));
    	dis[1] = 0;
    	while (!que.empty()) {
    		Node ans = que.top();
    		que.pop();
    		if (vis[ans.p]) continue;
    		vis[ans.p] = 1;
    		for (int i = 0; i < G[ans.p].size(); i++) {
    			int p = G[ans.p][i].p;
    			if (dis[p] > dis[ans.p] + G[ans.p][i].len) {
    				dis[p] = dis[ans.p] + G[ans.p][i].len;
    				que.push(Node(p, dis[p]));
    			}
    		}
    	}
    	return 0;
    }
    
    int main() {
    	
    	int be, en;
    	int len;
    	scanf("%d%d", &n, &m);
    	for (int i = 0; i < m; i++) {
    		scanf("%d %d %d", &be, &en, &len);
    		insert(be, en, len);
    		insert(en, be, len);
    	}
    	dijstra();
    	for (int i = 1; i <= n; i++) {
    		for (int j = 0; j < G[i].size(); j++) {
    			int be = i;
    			int en = G[i][j].p;
    			int len = G[i][j].len;
    			if (dis[be] + len == dis[en]) {
    				cnt[en]++;
    			}
    		}
    	}
    	long long ans = 1;
    	for (int i = 2; i <= n; i++) {
    		
    		ans = (ans*cnt[i]) % INF;
    	}
    	printf("%lld
    ", ans);
    	return 0;
    }
    

      

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  • 原文地址:https://www.cnblogs.com/lesning/p/11972715.html
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