UVA315- Network(无向图割点)
题意: 给出一张无向图,求割点的个数
思路:非常裸的题目。直接套用模版就可以。
代码:
#include <iostream> #include <cstdio> #include <cstring> #include <algorithm> using namespace std; const int MAXN = 1005; struct Edge{ int to, next; bool cut; }edge[MAXN * 10]; int head[MAXN], tot; int Low[MAXN], DFN[MAXN]; int Index, cnt; bool cut[MAXN]; void addedge(int u, int v) { edge[tot].to = v; edge[tot].next = head[u]; edge[tot].cut = false; head[u] = tot++; } void Tarjan(int u, int pre) { int v; Low[u] = DFN[u] = ++Index; int son = 0; for (int i = head[u]; i != -1; i = edge[i].next) { v = edge[i].to; if (v == pre) continue; if (!DFN[v]) { son++; Tarjan(v, u); if (Low[u] > Low[v]) Low[u] = Low[v]; if (u != pre && Low[v] >= DFN[u]) { cut[u] = true; } } else if (Low[u] > DFN[v]) Low[u] = DFN[v]; } if (u == pre && son > 1) cut[u] = true; } void init() { memset(head, -1, sizeof(head)); memset(DFN, 0, sizeof(DFN)); memset(cut, false, sizeof(cut)); tot = 0; Index = cnt = 0; } int main() { int n; while (scanf("%d", &n) && n) { init(); int u, v; while (scanf("%d", &u) && u) { char ch; while (scanf("%d%c", &v, &ch)) { addedge(u, v); addedge(v, u); if (ch == '\n') break; } } for (int i = 1; i <= n; i++) if (!DFN[i]) Tarjan(i, i); for (int i = 1; i <= n; i++) if (cut[i]) cnt++; printf("%d\n", cnt); } return 0; }
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