hdu 1874 畅通工程续

SPFA

 

#include<stdio.h>

#include<math.h>

#include<string.h>

#include<vector>

#include<algorithm>

using namespace std;

const int maxn = 2222;

vector<int>abc[maxn];

int s[maxn][maxn];

int js[maxn];

struct aaa{

    int s, node;

}dt[maxn];

bool cmp(const aaa&a, const aaa&b)

{

    return a.s<b.s;

}

int main()

{

    int n, m;

    while (~scanf("%d%d", &n, &m))

    {

        int i, u, v, ss, j;

        for (i = 0; i <= n; i++) for (j = 0; j <= n; j++) s[i][j] = 999999999;

        for (i = 0; i<maxn; i++) js[i] = 999999999;

        for (i = 0; i<maxn; i++) abc[i].clear();

        for (i = 1; i <= m; i++)

        {

            scanf("%d%d%d", &u, &v, &ss);

            if (ss<s[u][v])//选择最短的一条边

            {

                abc[u].push_back(v);

                s[u][v] = ss;

                abc[v].push_back(u);

                s[v][u] = ss;

            }

        }

        int sx, ex, b = 0;

        scanf("%d%d", &sx, &ex);

        js[sx] = 0;//第一个点

        dt[0].node = sx;

        dt[0].s = 0;

        for (i = 0; i <= b; i++)

        {

          //  sort(dt + i, dt + b, cmp);

            for (j = 0; j<abc[dt[i].node].size(); j++)

            {



                int yy = s[dt[i].node][abc[dt[i].node][j]];

                if (yy != 0)

                {

                    if (dt[i].s + yy<js[abc[dt[i].node][j]])

                    {

                        b++;

                        dt[b].node = abc[dt[i].node][j];

                        dt[b].s = dt[i].s + yy;

                        js[abc[dt[i].node][j]] = dt[i].s + yy;

                    }

                }



            }

        }

        if (js[ex] == 999999999)  printf("%d\n", -1);

        else printf("%d\n", js[ex]);

    }

    return 0;

}