hdu - 1874 - 畅通工程续（Dijkstra / SPFA）

#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;

const int maxn = 200 + 10;
const int INF = 1000000000;
int d[maxn][maxn], G[maxn][maxn];

int main()
{
int N, M, i, j, k, u, v, w, S, T;
while(scanf("%d%d", &N, &M) == 2)
{
for(i = 0; i < N; i++)
for(j = 0; j < N; j++)
G[i][j] = i == j ? 0 : INF;
for(i = 0; i < M; i++)      //建图
{
scanf("%d%d%d", &u, &v, &w);
G[u][v] = G[v][u] = min(G[u][v], w);        //最坑人的地方！！！
}

for(i = 0; i < N; i++)      //赋初值
for(j = 0; j < N; j++)
d[i][j] = i == j ? 0 : INF;

bool vis[maxn];
for(i = 0; i < N; i++)      //从i到任意点的最短距离
{
memset(vis, 0, sizeof(vis));
for(j = 0; j < N; j++)        //N次寻路
{
int x, y = INF;
for(k = 0; k < N; k++)
if(!vis[k] && d[i][k] <= y)
y = d[i][x = k];
vis[x] = 1;
for(k = 0; k < N; k++)
d[i][k] = min(d[i][k], d[i][x] + G[x][k]);
}
}

scanf("%d%d", &S, &T);
if(d[S][T] == INF) printf("-1\n");
else printf("%d\n", d[S][T]);
}
return 0;
}

#include <cstdio>
#include <queue>
#include <cstring>

using namespace std;

const int maxn = 2000 + 10;
const int maxm = 1000 + 10;
const int INF = 0x3f3f3f3f;
int head[maxn], nxt[maxm<<1], u[maxm<<1], v[maxm<<1], w[maxm<<1], d[maxn], S, T;
bool inq[maxn];

void addEdge(int uu, int vv, int ww, int e){
u[e] = uu;
v[e] = vv;
w[e] = ww;
nxt[e] = head[uu];
head[uu] = e;
}

void SPFA(){
memset(inq, 0, sizeof(inq));
memset(d, 0x3f, sizeof(d));
d[S] = 0;
queue<int> qu;
qu.push(S);
while(!qu.empty()){
int x = qu.front();
qu.pop();
inq[x] = 0;
for(int e = head[x]; e != -1; e = nxt[e]) if(d[v[e]] > d[x] + w[e]){
d[v[e]] = d[x] + w[e];
if(!inq[v[e]]){
qu.push(v[e]);
inq[v[e]] = 1;
}
}
}
}

int main()
{
int N, M, i, uu, vv, ww;
while(scanf("%d%d", &N, &M) == 2){
memset(head, -1, sizeof(head));
for(i = 0; i < M; i++){
scanf("%d%d%d", &uu, &vv, &ww);
addEdge(uu, vv, ww, 2*i);
addEdge(vv, uu, ww, 2*i+1);
}
scanf("%d%d", &S, &T);
SPFA();
int ret = (d[T] == INF) ? -1 : d[T];
printf("%d\n", ret);
}
return 0;
}