单源Dijksitra板子题
题目来源问 N 到 1 的最短距离

#include <iostream>
#include <algorithm>
#include <cstring>
#include <string>
#include <queue>
#include <vector>
#include <utility>
#include <cstdio>

#define IOS ios::sync_with_stdio(false),cin.tie(0),cout.tie(0)
#define endl '\n'

using namespace std;

typedef pair<int, int>pii;

const int inf = 0x3f3f3f3f;
const int N = 4e3 + 10;
const int M = 1e3 + 10;

int head[N], edge[N], ver[N], nxt[N], tot;

int t, n;
bool v[M];
int d[M];


void add(int x, int y, int v)
{
    ver[++tot] = y, edge[tot] = v, nxt[tot] = head[x], head[x] = tot;
    return;
}

void dijksitra()
{
    memset(d, 0x3f, sizeof(d));
    memset(v, 0, sizeof(v));
    d[1] = 0;
    priority_queue<pii>q;
    q.push(make_pair(0, 1));
    while (!q.empty())
    {
        int x = q.top().second;
        q.pop();
        if (v[x])
            continue;
        v[x] = 1;
        for (int i = head[x]; i; i = nxt[i])
        {
            int y = ver[i], z = edge[i];
            if (d[y] > d[x] + z)
            {
                d[y] = d[x] + z;
                q.push(make_pair(-d[y], y));
            }
        }
    }
    cout << d[n] << endl;
}

int main()
{
    IOS;

    cin >> t >> n;
    int x, y, z;
    for (int i = 1; i <= t; i++)
    {
        cin >> x >> y >> z;
        add(x, y, z), add(y, x, z);
    }
    dijksitra();
    return 0;
}