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BZOJ 3275 Number && 3158 千钧一发 最小割
题目大意:给出一些数字,要求选出一些数字并保证所有数字和最大,要求这其中的数字任意两个至少满足一个条件,则不能同时被选:1.这两个数的平方和是完全平方数。2.gcd(a,b) = 1。
思路:我们可以将奇数和偶数分开来讨论,奇数不满足1,偶数不满足2,所以奇数和奇数,偶数和偶数不会互相影响。之后O(n^2)的讨论其他数字对,有影响就连边,流量正无穷,最后跑最小割最最大获利。
CODE:
#define _CRT_SECURE_NO_WARNINGS #include <cmath> #include <queue> #include <cstdio> #include <cstring> #include <iostream> #include <algorithm> #define MAX 3010 #define MAXE 2000000 #define INF 0x3f3f3f3f #define S 0 #define T (MAX - 1) #define EPS 1e-7 using namespace std; struct MaxFlow{ int head[MAX],total; int next[MAXE],aim[MAXE]; long long flow[MAXE]; int deep[MAX]; MaxFlow():total(1) {} void Add(int x,int y,long long f) { next[++total] = head[x]; aim[total] = y; flow[total] = f; head[x] = total; } void Insert(int x,int y,long long f) { Add(x,y,f); Add(y,x,0); } bool BFS() { static queue<int> q; while(!q.empty()) q.pop(); memset(deep,0,sizeof(deep));; deep[S] = 1; q.push(S); while(!q.empty()) { int x = q.front(); q.pop(); for(int i = head[x]; i; i = next[i]) if(flow[i] && !deep[aim[i]]) { deep[aim[i]] = deep[x] + 1; q.push(aim[i]); if(aim[i] == T) return true; } } return false; } long long Dinic(int x,long long f) { if(x == T) return f; long long temp = f; for(int i = head[x]; i; i = next[i]) if(flow[i] && temp && deep[aim[i]] == deep[x] + 1) { long long away = Dinic(aim[i],min(flow[i],temp)); if(!away) deep[aim[i]] = 0; flow[i] -= away; flow[i^1] += away; temp -= away; } return f - temp; } }solver; int cnt; pair<int,int> odd[MAX],even[MAX]; int odds,evens; int energy[MAX]; int gcd(int x,int y) { return (y ? gcd(y,x % y):x); } inline bool Judge(int x,int y) { long long aim = (long long)x * x + (long long)y * y; if((long long)(sqrt(aim) + EPS) * (long long)(sqrt(aim) + EPS) == (long long)x * x + (long long)y * y) return true; return false; } int main() { cin >> cnt; long long ans = 0; for(int x,i = 1; i <= cnt; ++i) { scanf("%d",&x); if(x&1) odd[++odds] = make_pair(x,i); else even[++evens] = make_pair(x,i); } for(int i = 1; i <= cnt; ++i) scanf("%d",&energy[i]),ans += energy[i]; for(int i = 1; i <= odds; ++i) solver.Insert(S,i,energy[odd[i].second]); for(int i = 1; i <= evens; ++i) solver.Insert(odds + i,T,energy[even[i].second]); for(int i = 1; i <= odds; ++i) for(int j = 1; j <= evens; ++j) if(gcd(odd[i].first,even[j].first) == 1 && Judge(odd[i].first,even[j].first)) solver.Insert(i,odds + j,INF); long long max_flow = 0; while(solver.BFS()) max_flow += solver.Dinic(S,INF); cout << ans - max_flow << endl; return 0; }
BZOJ 3275 Number && 3158 千钧一发 最小割
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