[USACO 2004DEC] Navigation Nightmare

Posted 2021-01-13 evenbao

[题目链接]

          https://www.lydsy.com/JudgeOnline/problem.php?id=3362

[算法]

        带权并查集

        时间复杂度 : O(NlogN)

[代码]

         

#include<bits/stdc++.h>
using namespace std;
const int MAXN = 400010;

struct Que
{
        int f1 , f2 , t;
        int id;
} que[MAXN];

int n , m;
int f[MAXN] , dist[MAXN] , x[MAXN] , y[MAXN] , X[MAXN] , Y[MAXN] , d[MAXN];
int ans[MAXN];
char dir[MAXN][10];

template <typename T> inline void chkmax(T &x,T y) { x = max(x,y); }
template <typename T> inline void chkmin(T &x,T y) { x = min(x,y); }
template <typename T> inline void read(T &x)
{
    T f = 1; x = 0;
    char c = getchar();
    for (; !isdigit(c); c = getchar()) if (c == ‘-‘) f = -f;
    for (; isdigit(c); c = getchar()) x = (x << 3) + (x << 1) + c - ‘0‘;
    x *= f;
}
inline bool cmp(Que a,Que b)
{
        return a.t < b.t;
}
inline int get_root(int x)
{
        if (f[x] == x) return x;
        int fa = get_root(f[x]);
        X[x] += X[f[x]];
        Y[x] += Y[f[x]];
        return f[x] = fa;        
}

int main()
{
        
        scanf("%d%d",&n,&m);
        for (int i = 1; i <= n; i++) f[i] = i;
        for (int i = 1; i <= m; i++) scanf("%d%d%d%s",&x[i],&y[i],&d[i],&dir[i]);
        int q;
        read(q);
        for (int i = 1; i <= q; i++) 
        {
                scanf("%d%d%d",&que[i].f1 , &que[i].f2 , &que[i].t);
                que[i].id = i;
        }    
        sort(que + 1,que + q + 1,cmp);
        int cur = 1;
        for (int i = 1; i <= q; i++)
        {
                while (cur <= que[i].t)
                {
                        int sx = get_root(x[cur]) , sy = get_root(y[cur]);
                        if (sx == sy) continue;
                        f[sx] = sy;
                        if (dir[cur][0] == ‘E‘)
                        {
                                X[sx] = -X[x[cur]] + X[y[cur]] - d[cur];
                                Y[sx] = -Y[x[cur]] + Y[y[cur]];
                        }
                        if ( dir[cur][0] == ‘W‘ )
                        {
                                X[sx] = -X[x[cur]] + X[y[cur]] + d[cur];
                                Y[sx] = -Y[x[cur]] + Y[y[cur]];
                        }
                         if (dir[cur][0] == ‘N‘)
                      {
                                Y[sx] = -Y[x[cur]] + Y[y[cur]] - d[cur];
                                X[sx] = -X[x[cur]] + X[y[cur]] ;
                     }
                     if (dir[cur][0] == ‘S‘)
                     {
                                Y[sx] = -Y[x[cur]] + Y[y[cur]] + d[cur];
                                X[sx] = -X[x[cur]] + X[y[cur]];
                        }
                        ++cur;    
                }        
                if (get_root(que[i].f1) != get_root(que[i].f2)) ans[que[i].id] = -1;
                else ans[que[i].id] = abs(X[que[i].f1] - X[que[i].f2]) + abs(Y[que[i].f1] - Y[que[i].f2]);
        }
        for (int i = 1; i <= q; i++) printf("%d
",ans[i]);
        
        return 0;
    
}