SDUT 2143 - 图结构练习——最短路径（dijkstra+模板）

题目链接

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http://acm.sdut.edu.cn/onlinejudge2/index.php/Home/Index/problemdetail/pid/2143.html

题目大意

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就是求一个带权无向图的最短路径。

解题过程

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之前看啊哈算法学了下dijkstra，然后嫌麻烦一直没用过。现在看了个视频才发现，用优先队列优化后，非常好用，比SPFA还容易写，于是放出来做个模板。

题目分析

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略

AC代码

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#include<bits/stdc++.h>
using namespace std;

const int MAX = 100+10;

vector<pair<int, int> > edges[MAX];
int d[MAX];

int main()
{
    int n, m;
    while (~scanf("%d %d", &n, &m))
    {
        for (int i = 1; i <= n; i++)
        {
            edges[i].clear();
            d[i] = 1e9;
        }

        for (int i = 0; i < m; i++)
        {
            int u, v, w;
            scanf("%d %d %d", &u, &v, &w);
            edges[u].push_back(make_pair(v, w));
            edges[v].push_back(make_pair(u, w));
        }

        int s = 1, t = n;

        priority_queue<pair<int, int> >q;
        d[s] = 0;
        q.push(make_pair(-d[s], s));

        while (!q.empty())
        {
            int u = q.top().second;
            q.pop();
            for (int i = 0; i < edges[u].size(); i++)
            {
                int v = edges[u][i].first;
                if (d[v] > d[u] + edges[u][i].second)
                {
                    d[v] = d[u] + edges[u][i].second;
                    q.push(make_pair(-d[v], v));
                }
            }
        }

        if (d[t] == 1e9)
            printf("-1\n");
        else
            printf("%d\n", d[t]);
    }
}