59 lines
1.4 KiB
C++
59 lines
1.4 KiB
C++
#include <bits/stdc++.h>
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using namespace std;
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const int INF = 0x3f3f3f3f;
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const int N = 2510; //结点数
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const int M = 6200 * 2 + 10; //边数
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int n, m; // n个结点，m条边
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int s, t; //起点，终点
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//邻接表
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int h[N], e[M], w[M], ne[M], idx;
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void add(int a, int b, int c) {
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e[idx] = b, w[idx] = c, ne[idx] = h[a], h[a] = idx++;
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}
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int d[N]; //最短距离数组
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bool st[N]; //是不是进过队列
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// spfa模板
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void spfa(int start) {
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//将所有距离初始化为无穷大
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memset(d, 0x3f, sizeof d);
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//出发点的距离清零
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d[start] = 0;
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queue<int> q;
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q.push(start); //出发点入队列
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st[start] = true; //出发点标识已使用
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while (q.size()) {
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int t = q.front();
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q.pop();
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st[t] = false;
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for (int i = h[t]; ~i; i = ne[i]) {
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int j = e[i];
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if (d[j] > d[t] + w[i]) {
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d[j] = d[t] + w[i];
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if (!st[j]) {
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st[j] = true;
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q.push(j);
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}
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}
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}
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}
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}
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int main() {
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memset(h, -1, sizeof h);
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cin >> n >> m >> s >> t;
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for (int i = 0; i < m; i++) {
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int a, b, c;
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cin >> a >> b >> c;
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add(a, b, c), add(b, a, c);
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}
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spfa(s);
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cout << d[t] << endl;
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return 0;
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}
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