HDU 3038 How Many Answers Are Wrong 解題報告

Question Link

AC code

#include<iostream>
#include<queue>
#include<cstring>
#include<string>
#include<sstream>
#include<map>
#include<vector>
#include<cstdio>
#include<iostream>
#include<cmath>
#include<algorithm>
#include<cstdlib>
#include<stack>
#include<ctime>
using namespace std; 
#define rep(i,aa,bb) for(register int i=aa;i<=bb;i++)
#define rrep(i,aa,bb) for(register int i=aa;i>=bb;i--)
#define mset(var,val)	 memset(var,val,sizeof(var))
#define LL long long 
#define eps 0.000001
#define inf 0x7f7f7f7f
#define llinf 1e18
#define exp 0.000001
#define pai 3.141592654
#define random(x)   rand()%(x)
#define lowbit(x)   x&(-x)
inline int read()
{
	int x=0,y=1;char a=getchar();while ( a>'9' || a<'0'){if ( a=='-')y=-1;a=getchar();}
	while ( a>='0' && a<='9' ){	x=(x<<3)+(x<<1)+a-'0'; a=getchar();}return x*y;
}
#define N	200009
int fa[N],dis[N];
int n,m,ans; 
void init(){
	rep(i,1,N-8)	fa[i] = i , dis[i] = 0; 
	ans = 0 ;
}
int findfa( int x ){
	if ( x == fa[x]	 )	return x; 
	int xfa = fa[ x ];		
	fa[ x ] = findfa( fa[x] );
	dis[ x ] = dis[ x ] + dis[ xfa ];
	return fa[x];
}
void unin(int a , int b ,int s ){
	int afa = findfa(a);
	int bfa = findfa(b);
	if ( afa == bfa ){
		if ( dis[ a ] + s != dis[ b ])
			ans++; 
		return; 
	}
	else {
		fa[ bfa ] = afa; 
		dis[ bfa ] = - dis[ b ] + s + dis[ a ];
 	}
}
int main()
{
//	freopen("1.txt","r",stdin);
	while ( scanf("%d%d",&n,&m)  != EOF ){
		init();
		rep(aaai,1,m){
			int ai,bi,si; 
			ai = read(); bi = read(); si = read();
			unin(ai,bi+1,si);
		}
		cout<<ans<<endl; 
	}

	return 0;
}  

題目分析

dis表示距離，也是有向的，由 l 到 r 。 區間縮成兩個點，維護必要，左閉右開