• POJ 1379 Run Away(模拟退火)


    模拟退火的步骤:

    确定初始解集S和控制参数初值delta开始,对当前解重复的产生新解,并选择接受或舍弃,并逐步衰减delta值,算法终止后可以得到一组解集。答案可以最终解集的最优解。

    对于这道题,选择矩形内的一点,使得满足与给定点集的最小距离最大。同样可以用模拟退火算法来解决。

    # include <cstdio>
    # include <cstring>
    # include <cstdlib>
    # include <iostream>
    # include <vector>
    # include <queue>
    # include <stack>
    # include <map>
    # include <set>
    # include <cmath>
    # include <algorithm>
    using namespace std;
    # define lowbit(x) ((x)&(-x))
    # define pi 3.1415926535
    # define eps 1e-3
    # define MOD 1000000007
    # define INF 1000000000
    # define mem(a,b) memset(a,b,sizeof(a))
    # define FOR(i,a,n) for(int i=a; i<=n; ++i)
    # define FO(i,a,n) for(int i=a; i<n; ++i)
    # define bug puts("H");
    # define lch p<<1,l,mid
    # define rch p<<1|1,mid+1,r
    # define mp make_pair
    # define pb push_back
    typedef pair<int,int> PII;
    typedef vector<int> VI;
    # pragma comment(linker, "/STACK:1024000000,1024000000")
    typedef long long LL;
    inline int Scan() {
        int x=0,f=1;char ch=getchar();
        while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
        while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
        return x*f;
    }
    void Out(int a) {
        if(a<0) {putchar('-'); a=-a;}
        if(a>=10) Out(a/10);
        putchar(a%10+'0');
    }
    const int N=100005;
    //Code begin...
    
    struct Node{double x, y;}node[1005], now[15], tmp, tt, ans;
    int m;
    double d[15], total;
    
    inline double Rand(){return (rand()%1000+1)/1000.0;}
    inline double dis(Node a, Node b){return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));}
    inline double cal(Node p){
        double res=INF;
        FOR(i,1,m) res=min(res,dis(p,node[i]));
        return res;
    }
    int main ()
    {
        srand(10086);
        int T, x, y;
        scanf("%d",&T);
        while (T--) {
            total=0;
            scanf("%d%d%d",&x,&y,&m);
            FOR(i,1,m) scanf("%lf%lf",&node[i].x,&node[i].y);
            FOR(i,1,10) {
                now[i].x=Rand()*x; now[i].y=Rand()*y;
                d[i]=INF; FOR(j,1,m) d[i]=min(d[i],dis(now[i],node[j]));
            }
            double Tc=10000, alpha, v;
            while (Tc>eps) {
                FOR(i,1,10) {
                    tmp=now[i];
                    FOR(j,1,30) {
                        alpha=2.0*pi*Rand();
                        tt.x=tmp.x+Tc*cos(alpha); tt.y=tmp.y+Tc*sin(alpha);
                        if (tt.x<0||tt.x>x||tt.y<0||tt.y>y) continue;
                        if ((v=cal(tt))>d[i]) d[i]=v, now[i]=tt;
                    }
                }
                Tc*=0.9;
            }
            total=0;
            FOR(i,1,10) if (total<d[i]) total=d[i], ans=now[i];
            printf("The safest point is (%.1f, %.1f).
    ",ans.x,ans.y);
        }
        return 0;
    }
    View Code
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  • 原文地址:https://www.cnblogs.com/lishiyao/p/6715256.html
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