SSL2510&BZOJ1706 奶牛接力 矩阵

比较裸的邻接矩阵自乘,但因为是最小长度因此把*改成加

#include<iostream>#include<cstdio>#include<cstring>#include<cmath>#include<cstdlib>#include<algorithm>#define LL long long#define fo(i,a) for(int i=0;i<a;i++)using namespace std;inline LL read(){LL d=0,f=1;char s=getchar();while(s<'0'||s>'9'){if(s=='-')f=-1;s=getchar();}while(s>='0'&&s<='9'){d=d*10+s-'0';s=getchar();}return d*f;}#define N 105#define M 1005int nm,n=0,m,s,e;int tot[M];struct matrix{int a[N][N];void clear(){memset(a,0,sizeof(a));}void chu(){memset(a,60,sizeof(a));}void OUT(){fo(i,n){fo(j,n)cout<<a[i][j]<<' ';cout<<endl;}cout<<endl;}matrix operator*(const matrix b)const{matrix anss;anss.chu();fo(i,n)fo(j,n){fo(k,n){anss.a[i][j]=min(anss.a[i][j],a[i][k]+b.a[k][j]);}}return anss;}}I,A;void getI(){I.clear();fo(i,n)fo(j,n)if(i==j)I.a[i][j]=1;}int get(int k){if(tot[k]==-1)tot[k]=n++;return tot[k];}matrix KSM(matrix a,int k){matrix ret=a;k--;while(k){if(k&1)ret=a*ret;a=a*a;k>>=1;}return ret;}int main(){memset(tot,-1,sizeof(tot));A.chu();nm=read();m=read();s=read(),e=read();fo(i,m){int w=read(),x=read(),y=read();x=get(x),y=get(y);A.a[x][y]=A.a[y][x]=w;}s=get(s);e=get(e);getI();matrix ans=KSM(A,nm);//A.OUT();ans.OUT();cout<<ans.a[s][e]<<endl;return 0;}