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POJ 2749 二分+2-sat判定

热度:9   发布时间:2024-01-13 17:56:31.0

这题还是挺好想建图的 二分判定就行了


#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#define MAXN 2005
#define MAXM 50005
#define INF 1000000000
using namespace std;
vector<int>g[MAXN];
int n, A, B;
int hatex[MAXN], hatey[MAXN], frix[MAXN], friy[MAXN];
int scc, index;
int low[MAXN], dfn[MAXN], instack[MAXN], fa[MAXN];
stack<int>st;
struct P
{int x, y;
}s1, s2, p[MAXN];
void init()
{for(int i = 0; i < MAXN; i++) g[i].clear();memset(dfn, 0, sizeof(dfn));while(!st.empty()) st.pop();memset(instack, 0, sizeof(instack));scc = index = 0;
}
void tarjan(int u)
{dfn[u] = low[u] = ++index;instack[u] = 1;st.push(u);int v;int size = g[u].size();for(int i = 0; i < size; i++){v = g[u][i];if(!dfn[v]){tarjan(v);low[u] = min(low[u], low[v]);}else if(instack[v]) low[u] = min(low[u], dfn[v]);}if(dfn[u] == low[u]){scc++;do{v = st.top();st.pop();fa[v] = scc;instack[v] = 0;}while(v != u);}
}
int dist(P a, P b)
{return abs(a.x - b.x) + abs(a.y - b.y);
}
void build(int mid)
{for(int i = 1; i <= n; i++)for(int j = i + 1; j <= n; j++){if(dist(p[i], s1) + dist(p[j], s1) > mid){g[i].push_back(j + n);g[j].push_back(i + n);}if(dist(p[i], s2) + dist(p[j], s2) > mid){g[i + n].push_back(j);g[j + n].push_back(i);}if(dist(s1, s2) + dist(p[i], s1) + dist(p[j], s2) > mid){g[i].push_back(j);g[j + n].push_back(i + n);}if(dist(s1, s2) + dist(p[i], s2) + dist(p[j], s1) > mid){g[i + n].push_back(j + n);g[j].push_back(i);}}for(int i = 1; i <= A; i++){g[hatex[i]].push_back(hatey[i] + n);g[hatey[i]].push_back(hatex[i] + n);g[hatex[i] + n].push_back(hatey[i]);g[hatey[i] + n].push_back(hatex[i]);}for(int i = 1; i <= B; i++){g[frix[i]].push_back(friy[i]);g[frix[i] + n].push_back(friy[i] + n);g[friy[i]].push_back(frix[i]);g[friy[i] + n].push_back(frix[i] + n);}
}
bool check()
{for(int i = 1; i <= 2 * n; i++)if(!dfn[i]) tarjan(i);for(int i = 1; i <= n; i++)if(fa[i] == fa[i + n]) return false;return true;
}
void solve()
{int low = 0, high = INF, ans = INF;while(low <= high){int mid = (low + high) >> 1;init();build(mid);if(check()) {high = mid - 1; ans = min(ans, mid);}else low = mid + 1;}if(ans != INF)printf("%d\n", ans);else puts("-1");
}
int main()
{while(scanf("%d%d%d", &n, &A, &B) != EOF){scanf("%d%d%d%d", &s1.x, &s1.y, &s2.x, &s2.y);for(int i = 1; i <= n; i++) scanf("%d%d", &p[i].x, &p[i].y);for(int i = 1; i <= A; i++) scanf("%d%d", &hatex[i], &hatey[i]);for(int i = 1; i <= B; i++) scanf("%d%d", &frix[i], &friy[i]);solve();}return 0;
}