codeforces 505B——DFS——Mr. Kitayuta's Colorful Graph
Mr. Kitayuta has just bought an undirected graph consisting of n vertices and m edges. The vertices of the graph are numbered from 1 ton. Each edge, namely edge i, has a color ci, connecting vertex ai and bi.
Mr. Kitayuta wants you to process the following q queries.
In the i-th query, he gives you two integers — ui and vi.
Find the number of the colors that satisfy the following condition: the edges of that color connect vertex ui and vertex vi directly or indirectly.
Input
The first line of the input contains space-separated two integers — n and m (2 ≤ n ≤ 100, 1 ≤ m ≤ 100), denoting the number of the vertices and the number of the edges, respectively.
The next m lines contain space-separated three integers — ai, bi (1 ≤ ai < bi ≤ n) and ci (1 ≤ ci ≤ m). Note that there can be multiple edges between two vertices. However, there are no multiple edges of the same color between two vertices, that is, if i ≠ j, (ai, bi, ci) ≠ (aj, bj, cj).
The next line contains a integer — q (1 ≤ q ≤ 100), denoting the number of the queries.
Then follows q lines, containing space-separated two integers — ui and vi (1 ≤ ui, vi ≤ n). It is guaranteed that ui ≠ vi.
Output
For each query, print the answer in a separate line.
Sample Input
4 5
1 2 1
1 2 2
2 3 1
2 3 3
2 4 3
3
1 2
3 4
1 4
2
1
0
5 7
1 5 1
2 5 1
3 5 1
4 5 1
1 2 2
2 3 2
3 4 2
5
1 5
5 1
2 5
1 5
1 4
1
1
1
1
2
Hint
Let's consider the first sample.
- Vertex 1 and vertex 2 are connected by color 1 and 2.
- Vertex 3 and vertex 4 are connected by color 3.
- Vertex 1 and vertex 4 are not connected by any single color.
/* 题意:求从i到j有几条能通过的(颜色相同)的路径 多开一维保存颜色,暴力搜索 对节点i,j对不同颜色进行dfs */ #include <cstdio> #include <cstring> #include <algorithm> #include <vector> using namespace std; int map[110][110]; int vis[110]; int vis1[110][110]; int color[110][110][110]; vector<int> G[110]; int sum; bool dfs(int u,int vv,int color1) { if(!vis[u]){ vis[u] = 1; if(u == vv) return true; for(int i = 0 ; i < G[u].size(); i++){ int v = G[u][i]; for(int j = 1 ; j <= vis1[u][v]; j++){ if(color[u][v][j] == color1){ if( dfs(v, vv, color1)) return true; } } } } return false ; } int main() { int n, m, k; int a, b, c; while(~scanf("%d %d", &n, &m)){ memset(vis, 0, sizeof(vis1)); for(int i= 1; i <= m; i++){ scanf("%d%d%d", &a, &b, &c); G[a].push_back(b); G[b].push_back(a); vis1[a][b]++; vis1[b][a]++; color[a][b][vis1[a][b]] = c; color[b][a][vis1[b][a]] = c; } scanf("%d", &k); int v1, v2; while(k--){ sum = 0; scanf("%d%d", &v1, &v2); for(int i = 1; i <= m; i++){ memset(vis, 0, sizeof(vis)); if(dfs(v1, v2, i)){ sum++; } } printf("%d\n", sum); } } return 0; }