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ID题目提交者结果用时内存语言文件大小提交时间测评时间
#214262#2763. 幻想乡的拜访KXG1002803ms85180kbC++11994b2024-11-16 20:59:552024-11-16 23:13:18

answer

#include <cstdio>
#include <vector>
using namespace std;
const int mod = 1e9 + 7;
int n, u, v;
vector<int> G[1000010];
long long dp1[1000010], dp2[1000010], siz[1000010];
void dfs(int u, int fa) {
    siz[u] = u;
    for (int v : G[u]) {
        if (v == fa) continue;
        dfs(v, u);
        siz[u] += siz[v];
        dp1[u] += dp1[v] + siz[v];
    }
}
void dfs2(int u, int fa) {
    for (int v : G[u]) {
        if (v == fa) continue;
        dp2[v] = dp2[u] - siz[v] + (siz[1] - siz[v]);
        dfs2(v, u);
    }
}
int main() {
    scanf("%d", &n);
    for (int i = 1; i < n; i++) {
        scanf("%d%d", &u, &v);
        G[u].push_back(v);
        G[v].push_back(u);
    }
    dfs(1, -1);
    dp2[1] = dp1[1];
    dfs2(1, -1);
    long long ans = 0;
    for (int i = 1; i <= n; i++) {
        dp2[i] %= mod;
        ans += i * dp2[i] % mod;
    }
    ans %= mod;
    ans = ans * ((mod + 1) / 2) % mod;
    printf("%lld\n", ans);
    return 0;
}

详细

小提示:点击横条可展开更详细的信息

Test #1:

score: 10
Accepted
time: 3ms
memory: 24540kb

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: 8ms
memory: 24540kb

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: 8ms
memory: 24544kb

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: 8ms
memory: 24712kb

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: 9ms
memory: 24712kb

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: 4ms
memory: 24712kb

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: 613ms
memory: 85164kb

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: 650ms
memory: 85008kb

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: 902ms
memory: 85180kb

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: 598ms
memory: 85136kb

input:

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

output:

201471911

result:

ok single line: '201471911'