7-2 最小生成树-kruskal算法 分数 15
const int maxn = 1000;
struct edge {int u, v, w;
}e[maxn];
int n, m, f[30];
bool cmp(edge a, edge b) {return a.w < b.w;
}
int find(int x) {if (f[x] == x) {return x;}else {f[x] = find(f[x]);return f[x];}
} //int arr[100];//int n;//cin >> n;//for (int i = 1; i <= n; i++)cin >> arr[i];
cin >> n >> m;
for (int i = 1; i <= n; i++)f[i] = i;
for (int i = 1; i <= m; i++) {cin >> e[i].u >> e[i].v >> e[i].w;
}
sort(e + 1, e + m + 1, cmp);
for (int i = 1; i <= m; i++) {int a = find(e[i].u), b = find(e[i].v);if (a != b) {f[a] = b;if (e[i].u > e[i].v) { cout << e[i].v << "," << e[i].u << "," << e[i].w << endl; }else {cout << e[i].u << "," << e[i].v << "," << e[i].w << endl;}}else {continue;}
}
7-1 校园最短路径 分数 10
主要是怎么打印路径，以及输入的格式，怎么转换这个输入格式
用pre数组，用string,然后在string里，用find,用字符下标，都转换为int型
链式前向星+堆优化dij
用pre数组记录前驱节点的索引，就是在string里的下标，也通过string类里的find函数找到相应字符的下标
#include <iostream>
#include <vector>
#include <algorithm>
#include<stack>
#include<queue>
#include <unordered_map>
#include<string>
#include<cstdio>
#include<map>
using namespace std;
struct edge {int v, w, next;
}e[102];
int h[102], n, m, pre[102], dis[102], cnt = 0;
string s;
bool vis[102] = { 0 };
void add(int u, int v, int w) {e[++cnt].v = v;e[cnt].w = w;e[cnt].next = h[u];h[u] = cnt;
}
void print(int x) {if (!x) {cout << s[0];return;}print(pre[x]);cout << "->" << s[x];
}
typedef pair<int, int>pii;
priority_queue<pii, vector<pii>, greater<pii>>q;
int main() {cin >> n >> m >> s;for (int i = 0; i < n; i++)dis[i] = 1e8;for (int i = 1; i <= m; i++) {string a;int w;cin >> a >> w;add(s.find(a[0]), s.find(a[1]), w);add(s.find(a[1]), s.find(a[0]), w);}dis[0] = 0, vis[0] = 1, pre[0] = -1;for (int i = h[0]; i; i = e[i].next) {dis[e[i].v] = e[i].w;q.push({ dis[e[i].v],e[i].v });pre[e[i].v] = 0;}while (!q.empty()) {int d = q.top().first, u = q.top().second;q.pop();if (vis[u])continue;vis[u] = 1;for (int i = h[u]; i; i = e[i].next) {int v = e[i].v;if (dis[v] > dis[u] + e[i].w) {dis[v] = dis[u] + e[i].w;q.push({ dis[v], v });pre[v] = u;}}}for (int i = 0; i < n; i++) {if (dis[i] >= 1e8) {cout << "dist[" << s[0] << "][" << s[i] << "]=" << 256 << endl;cout << s[i] << endl;}else {cout << "dist[" << s[0] << "][" << s[i] << "]=" << dis[i] << endl;print(i);cout << endl;}}return 0;
}邻接矩阵+朴素dij
#include <iostream>
#include <vector>
#include <algorithm>
#include<stack>
#include<queue>
#include <unordered_map>
#include<string>
#include<cstdio>
#include<map>
using namespace std;
int g[1000][1000], dis[1000], pre[1000], n, m;
bool vis[1000] = { 0 };
string s;
void print(int x) {if (pre[x] == -1) {cout << s[0];return;}print(pre[x]);cout << "->" << s[x];
}
int main() {cin >> n >> m;cin >> s;for(int i=0;i<n;i++){for(int j=0;j<n;j++){g[i][j]=1e8;}}for (int i = 0; i < n; i++)dis[i] = 1e8;for (int i = 1; i <= m; i++) {string a;int w;cin >> a >> w;int j = s.find(a[0]), k = s.find(a[1]);g[j][k] = w;g[k][j] = w;}dis[0] = 0, pre[0] = -1;for (int i = 1; i <= n - 1; i++) {if (g[0][i])dis[i] = g[0][i];}for (int i = 1; i <= n - 1; i++) {int u = -1;for (int j = 1; j <= n - 1; j++) {if (!vis[j] && (u == -1 || dis[u] > dis[j])) {u = j;}}vis[u] = 1;for (int j = 1; j <= n - 1; j++) {if (dis[j] >dis[u] + g[u][j]) {pre[j] = u;dis[j] = dis[u] + g[u][j];}}}for (int i = 0; i < n; i++) {if (dis[i] >= 1e8) {cout << "dist[" << s[0] << "][" << s[i] << "]=" << 256 << endl;cout << s[i] << endl;}else {cout << "dist[" << s[0] << "][" << s[i] << "]=" << dis[i] << endl;print(i);cout << endl;}}return 0;
}
