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BZOJ3362 [Usaco2004 Feb]Navigation Nightmare 导航噩梦

2016年09月24日 ⁄ 综合 ⁄ 共 2426字 ⁄ 字号 评论关闭

题目大意:自行脑补。

思路:维护两个维度上的带权并查集即可。

注意对于题目给出的一堆关系,我们应该添加两对关系。

Code:

#include
<cstdio>
#include
<cstring>
#include
<cctype>
#include
<iostream>
#include
<algorithm>
using

namespace

std;
 
#define
N 40010
int

n, m;
struct

UnionSet {
    int

root[N], dis[N];
    void

reset() {
        int

i;
        for(i
= 1; i <= n; ++i)
            root[i]
= i, dis[i] = 0;
    }
    int

find(
int

x) {
        static

int

stack[N];
        int

top = 0;
        for(;
x != root[x]; x = root[x])
            stack[++top]
= x;
        for(int

i = top - 1; i >= 1; --i)
            dis[stack[i]]
+= dis[stack[i + 1]], root[stack[i]] = x;
        return

x;
    }
}Set[2];
 
#define
K 10010
struct

Ask {
    int

u, v, tclock, lab;
    void

read(
int

_) {
        lab
= _;
        scanf("%d%d%d",
&u, &v, &tclock);
    }
    bool

operator < (
const

Ask &B)
const

{
        return

tclock < B.tclock;
    }
}S[K];
int

ans[K];
 
#define
M 40010
int

u[M], v[M], d[M];
bool

vec[M];
 
#define
_abs(x) ((x)>0?(x):-(x))
 
int

main() {
    #ifndef
ONLINE_JUDGE
    freopen("tt.in",
"r",
stdin);
    #endif
     
    scanf("%d%d",
&n, &m);
     
    register

int

i, j;
     
    int

a, b, x;
    char

s[10];
    for(i
= 1; i <= m; ++i) {
        scanf("%d%d%d%s",
&a, &b, &x, s);
        d[i]
= x;
        if

(s[0] ==
'E')
            u[i]
= a, v[i] = b, vec[i] = 0;
        else

if

(s[0] ==
'W')
            u[i]
= b, v[i] = a, vec[i] = 0;
        else

if

(s[0] ==
'N')
            u[i]
= a, v[i] = b, vec[i] = 1;
        else
            u[i]
= b, v[i] = a, vec[i] = 1;
    }
     
    int

Q;
    scanf("%d",
&Q);
    for(i
= 1; i <= Q; ++i)
        S[i].read(i);
    sort(S
+ 1, S + Q + 1);
     
    Set[0].reset(),
Set[1].reset();
     
    int

ra, rb;
    j
= 1;
    for(i
= 1; i <= m; ++i) {
        ra
= Set[vec[i]].find(u[i]);
        rb
= Set[vec[i]].find(v[i]);
        Set[vec[i]].root[ra]
= rb;
        Set[vec[i]].dis[ra]
= d[i] + Set[vec[i]].dis[v[i]] - Set[vec[i]].dis[u[i]];
         
        ra
= Set[1 - vec[i]].find(u[i]);
        rb
= Set[1 - vec[i]].find(v[i]);
        Set[1
- vec[i]].root[ra] = rb;
        Set[1
- vec[i]].dis[ra] = Set[1 - vec[i]].dis[v[i]] - Set[1 - vec[i]].dis[u[i]];
         
        for(;
S[j].tclock == i; ++j) {
            ra
= Set[0].find(S[j].u), rb = Set[0].find(S[j].v);
            if

(ra != rb) {
                ans[S[j].lab]
= -1;
                continue;
            }
            ans[S[j].lab]
+= _abs(Set[0].dis[S[j].u] - Set[0].dis[S[j].v]);
            ra
= Set[1].find(S[j].u), rb = Set[1].find(S[j].v);
            if

(ra != rb) {
                ans[S[j].lab]
= -1;
                continue;
            }
            ans[S[j].lab]
+= _abs(Set[1].dis[S[j].u] - Set[1].dis[S[j].v]);
        }
    }
     
    for(i
= 1; i <= Q; ++i)
        printf("%d\n",
ans[i]);
     
    return

0;
}

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