HD1874 畅通工程续

来源：互联网发布：python 3.5.2打开编辑：程序博客网时间：2024/06/15 01:38

思考：最短路入门题目，可以用求最短路的算法，数据量也不大，比如Dijkstra, floy 或者SPFA算法。

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#include <vector>#include <queue>using namespace std;const int maxn = 210;const int maxm = 1100;const int INF = 0x7fffffff;int gn, gm;bool inque[maxn];int dist[maxn];queue<int> Q;vector<pair<int, int> > g[maxn + 10];void spfa(const int s, const int t) {    int i;    memset(inque, false, sizeof(inque));    for(i = 0; i < gn; i++) dist[i] = INF;    dist[s] = 0;    while(!Q.empty()) Q.pop();//清空队列.    Q.push(s);    inque[s] = true;    while(!Q.empty()) {        int u = Q.front();        Q.pop();        for(i = 0; i < (int)g[u].size(); i++) {            int t = g[u][i].first;            if(dist[u] != INF && g[u][i].second != INF && dist[u]+g[u][i].second < dist[t]) {                dist[t] = dist[u] + g[u][i].second;                if(!inque[t]) {                    inque[t] = true;                    Q.push(t);                }            }        }        inque[u] = false;    }    if(dist[t] != INF) {        printf("%d\n", dist[t]);    }    else printf("-1\n");}void init() {    int i;    for(i = 0; i < maxn; i++) {        g[i].clear();    }}int main(){    int i;    int x, y, w;    pair<int,int> t;    while(scanf("%d%d", &gn, &gm) != EOF) {        init();//清空容器.        for(i = 0; i < gm; i++) {            scanf("%d%d%d", &x, &y, &w);            t.first = y;            t.second = w;            g[x].push_back(t);            t.first = x;            g[y].push_back(t);        }        int s, tt;        scanf("%d%d", &s, &tt);        spfa(s, tt);    }    return 0;}

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