AcWing 1129. 热浪（单源最短路）

题目链接

https://www.acwing.com/problem/content/1131/https://www.acwing.com/problem/content/1131/

题解

此题属于单源最短路问题，根据数据范围，可以使用Dijkstra算法、堆优化版的Dijkstra算法、SPFA算法。本例采用SPFA算法，使用手写循环队列来实现。

代码

#include <cstring>
#include <iostream>
#include <algorithm>using namespace std;const int N = 2510, M = 6200 * 2 + 10;int n, m, S, T;
int h[N], e[M], w[M], ne[M], idx;
int dist[N], q[N];
bool st[N];void add(int a, int b, int c)
{e[idx] = b, w[idx] = c, ne[idx] = h[a], h[a] = idx++;
}void spfa()
{memset(dist, 0x3f, sizeof dist);dist[S] = 0;int hh = 0, tt = 1;q[0] = S, st[S] = true;while (hh != tt){int t = q[hh++];if (hh == N) hh = 0;st[t] = false;for (int i = h[t]; ~i; i = ne[i]){int j = e[i];if (dist[j] > dist[t] + w[i]){dist[j] = dist[t] + w[i];if (!st[j]){q[tt++] = j;if (tt == N) tt = 0;st[j] = true;}}}}
}int main()
{cin >> n >> m >> S >> T;memset(h, -1, sizeof h);for (int i = 0; i < m; i++){int a, b, c;cin >> a >> b >> c;add(a, b, c), add(b, a, c);}spfa();cout << dist[T] << endl;return 0;
}

参考资料

1. AcWing算法提高课