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IDProblemSubmitterResultTimeMemoryLanguageFile sizeSubmit timeJudge time
#214260#2763. 幻想乡的拜访stawalr1001211ms59484kbC++799b2024-11-16 20:56:382024-11-16 23:13:09

answer

#include<cstdio>
#define int long long
using namespace std;
const int mn=1e6+5,mod=1e9+7;
int n,ans;
int hd[mn],to[mn<<1],nxt[mn<<1],cnt=1;
int f[mn],sz[mn];
void add(int x,int y)
{
    nxt[cnt]=hd[x];
    to[cnt]=y;
    hd[x]=cnt++;
}
void dfs(int x,int y)
{
    sz[x]=x;
    f[x]=0;
    for(int i=hd[x];i;i=nxt[i])
    {
        int u=to[i];
        if(u==y)continue;
        dfs(u,x);
        ans+=sz[x]*sz[u]%mod+sz[x]*f[u]%mod+sz[u]*f[x]%mod;
        ans%=mod;
        sz[x]+=sz[u];
        sz[x]%=mod;
        f[x]+=f[u]+sz[u];
        f[x]%=mod;
    }
}
signed main()
{
    int x,y;
    scanf("%lld",&n);
    for(int i=1;i<n;i++)
    {
        scanf("%lld%lld",&x,&y);
        add(x,y);
        add(y,x);
    }
    dfs(1,0);
    printf("%lld",ans);
}

Details

小提示:点击横条可展开更详细的信息

Test #1:

score: 10
Accepted
time: 0ms
memory: 544kb

input:

200
20 160
90 160
5 90
78 90
186 90
149 90
104 78
136 160
106 78
100 106
168 90
30 5
85 136
28 149
1...

output:

104425891

result:

ok single line: '104425891'

Test #2:

score: 10
Accepted
time: 0ms
memory: 544kb

input:

200
49 91
20 91
147 91
131 20
36 131
9 131
51 147
173 51
32 36
169 51
180 51
2 91
133 2
72 20
14 169...

output:

145567217

result:

ok single line: '145567217'

Test #3:

score: 10
Accepted
time: 0ms
memory: 544kb

input:

200
44 72
187 72
115 72
124 115
80 124
34 72
22 115
162 34
123 44
93 22
135 80
5 124
112 72
76 187
3...

output:

226420652

result:

ok single line: '226420652'

Test #4:

score: 10
Accepted
time: 0ms
memory: 704kb

input:

3000
940 1649
220 1649
1438 1649
2264 1649
1467 940
1825 220
1646 940
571 220
1419 220
2509 1438
264...

output:

781596579

result:

ok single line: '781596579'

Test #5:

score: 10
Accepted
time: 0ms
memory: 700kb

input:

3000
2156 216
2422 2156
2801 216
2504 2156
2701 2156
2582 2801
1558 2156
864 2582
737 864
2919 1558
...

output:

236427659

result:

ok single line: '236427659'

Test #6:

score: 10
Accepted
time: 0ms
memory: 700kb

input:

3000
2966 2885
2657 2885
2613 2966
1686 2613
2803 2885
191 2657
2824 2657
675 2657
2693 191
2798 191...

output:

688220644

result:

ok single line: '688220644'

Test #7:

score: 10
Accepted
time: 317ms
memory: 59468kb

input:

1000000
984750 990109
970095 984750
996126 970095
998081 990109
987074 970095
962711 970095
916630 9...

output:

192557796

result:

ok single line: '192557796'

Test #8:

score: 10
Accepted
time: 292ms
memory: 59356kb

input:

1000000
947305 936749
948062 947305
970449 947305
988744 948062
998703 988744
986194 947305
997762 9...

output:

160385007

result:

ok single line: '160385007'

Test #9:

score: 10
Accepted
time: 293ms
memory: 59484kb

input:

1000000
952012 962256
982471 962256
955412 952012
953636 962256
991390 952012
998704 953636
999294 9...

output:

308556344

result:

ok single line: '308556344'

Test #10:

score: 10
Accepted
time: 309ms
memory: 59452kb

input:

1000000
900864 972452
986047 900864
953966 972452
977801 986047
997024 972452
954755 953966
999240 9...

output:

201471911

result:

ok single line: '201471911'