BZOJ 2763

2763: [JLOI2011]飞行路线

spfa 跑分层图
妙～

BZOJ 2763

/**************************************************************
    Problem: 2763
    User: Dream_Tonight
    Language: C++
    Result: Accepted
    Time:3456 ms
    Memory:8844 kb
****************************************************************/
 
#include <algorithm>
#include <iostream>
#include <cstring>
#include <vector>
#include <string>
#include <cstdio>
#include <cmath>
#include <stack>
#include <queue>
#include <list>
#include <map>
#include <set>
 
 
using namespace std;
#define lson l , m , rt << 1
#define rson m + 1 , r , rt << 1 | 1
typedef long long ll;
typedef pair<int, int> pii;
const int maxn = 1e5 + 7;
const int inf = 2139062143;
const int mod = 100000000;
int n, m, k, s, t, z, y, x, cnt = 0;
int head[maxn], dis[maxn][15];
struct node {
    int to, value, next;
} edge[maxn];
 
void ins(int u, int v, int w) {
    edge[++cnt] = (node) {v, w, head[u]}, head[u] = cnt;
}
 
int spfa() {
    queue<pii> q;
    memset(dis, 127, sizeof(dis));
    q.push(make_pair(s, 0));
    dis[s][0] = 0;
    while (!q.empty()) {
        pii u = q.front();
        q.pop();
        for (int i = head[u.first]; i; i = edge[i].next) {
            int to = edge[i].to;
            if (dis[to][u.second] > dis[u.first][u.second] + edge[i].value) {
                dis[to][u.second] = dis[u.first][u.second] + edge[i].value;
                q.push(make_pair(to, u.second));
            }
            if (u.second + 1 <= k && dis[to][u.second + 1] > dis[u.first][u.second]) {
                dis[to][u.second + 1] = dis[u.first][u.second];
                q.push(make_pair(to, u.second + 1));
            }
        }
    }
    return dis[t][k];
}
 
int main() {
#ifndef ONLINE_JUDGE
    freopen("weather.in", "r", stdin);
#endif
    scanf("%d%d%d", &n, &m, &k);
    scanf("%d%d", &s, &t);
    for (int i = 0; i < m; i++) {
        scanf("%d%d%d", &x, &y, &z);
        ins(x, y, z);
        ins(y, x, z);
    }
    printf("%d", spfa());
    return 0;
}