[Uva] 539 - The Settlers of Catan

http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=480

图深度遍历水题, 千万别忘记visited标志位的重置.

#include <cstdio>
#include <cstring>
using namespace std;

int gn = 0;
int gm = 0;
int longest = 0;
#define MAX_N 26

typedef struct _graph {
    int nv;
    int ne;
    int ma[MAX_N][MAX_N];
    bool visited[MAX_N][MAX_N];
    _graph(int v, int e) {
        memset(ma, 0, sizeof(ma));
        resetVisited();
        nv = v;
        ne = e;
    }
    void addEdge(int a, int b) {
        ma[a][b] = 1;
        ma[b][a] = 1;
    }
    void resetVisited() {
        memset(visited, 0, sizeof(visited));
    }
}graph;

void dfs(graph& g, int s, int num) {
    if (num > longest) {
        longest = num;
    }
    for (int i = 0; i < g.nv; ++i) if (g.ma[s][i] && !g.visited[s][i] && !g.visited[i][s]) {
        g.visited[i][s] = g.visited[s][i] = true;
        dfs(g, i, num + 1);
        g.visited[i][s] = g.visited[s][i] = false;
    }
}

int main(int argc, const char * argv[])
{
    while (scanf("%d%d", &gn, &gm)) {
        if (gn == 0 && gm == 0) {
            break;
        }
        longest = 0;
        graph g(gn, gm);
        for (int i = 0; i < gm; ++i) {
            int a = 0, b = 0;
            scanf("%d%d", &a, &b);
            g.addEdge(a, b);
        }
        for (int i = 0; i < gn; ++i) {
            dfs(g, i, 0);
            g.resetVisited();
        }
        printf("%d\n", longest);
    }
    return 0;
}