今日语录：成功不是终点，失败不是致命，勇气才是取胜的关键。

prim算法

#include <cstring>
#include <algorithm>
#include <iostream>#define _CRT_SECURE_NO_WARNINGS
using namespace std;const int N = 510,INF = 0x3f3f3f3f;int n, m;
int g[N][N];
int dist[N];
bool st[N];int prim()
{memset(dist, 0x3f, sizeof dist);int res = 0;for (int i = 0; i < n; i++){int t = -1;for (int j = 1; j <= n; j++)if (!st[j] && (t == -1 || dist[t] > dist[j]))t = j;if (i && dist[t] == INF)return INF;if (i)res += dist[t];for (int j = 1; j <= n; j++)dist[j] = min(dist[j], g[t][j]);st[t] = true;}return res;
}int main()
{scanf("%d%d", &n, &m);memset(g, 0x3f, sizeof g);while (m--){int a, b,c;scanf("%d%d%d", &a, &b, &c);g[a][b] = g[b][a] = min(g[a][b], c);}int t = prim();if (t == INF)puts("impossible");else printf("%d\n", t);return 0;
}

kruskal算法(稀疏图)

#include <algorithm>
#include <iostream>#define _CRT_SECURE_NO_WARNINGS
using namespace std;const int N = 10010;int n, m;
int p[N];struct Edge
{int a, b, w;bool operator< (const Edge& W)const{return w < W.w;}
}edges[N];int find(int x)
{if (p[x] != x)p[x] = find(p[x]);return p[x];
}int main()
{scanf("%d%d", &n, &m);for (int i = 0; i < m; i++){int a, b, w;scanf("%d%d%d", &a, &b, &w);edges[i] = { a,b,w };}sort(edges, edges + m);for (int i = 1; i <= n; i++)p[i] = i;int res = 0, cnt = 0;//res存储最小生成树中的权重之和//cnt存储的是当前存储了多少条边for (int i = 0; i < m; i++){int a = edges[i].a, b = edges[i].b, w = edges[i].w;a = find(a), b = find(b);if (a != b){p[a] = b;res += w;cnt++;}}if (cnt < n - 1)puts("impossible");else printf("%d\n", res);return 0;
}