思路借鉴了之前的图的层数，发现这个贼好用；
关键在于输出浮点数的格式，这个要注意一下

#include<iostream>
#include<stdlib.h>
#include<stdio.h>
#include<vector>
#include<queue>
#include<math.h>
using namespace std;
using std::vector;
using std::queue;
const int maxn=100010;
struct node{
    double data;
    vector<int>child;
    int layer=0;
}Node[maxn];
int n;
double p,r;
vector<int>leaf;
void BFS(int x){
    int layer=0;
    queue<int>q;
    q.push(x);
    while(!q.empty()){
        layer++;
        int index;
        int length=q.size();
        for(int i=0;i<length;i++){
            index=q.front();
            q.pop();
            Node[index].layer=layer;
            for(int j=0;j<Node[index].child.size();j++){
                q.push(Node[index].child[j]);
            }
        }
    }
}

int main(){
    int num;
    scanf("%d%lf%lf",&n,&p,&r);
    for(int i=0;i<n;i++){
        scanf("%d",&num);
        if(num==0){
            scanf("%lf",&Node[i].data);
            leaf.push_back(i);
        }else{
            for(int j=0;j<num;j++){
                int child;
                scanf("%d",&child);
                Node[i].child.push_back(child);
            }
        }
    }
    BFS(0);
    double sum;
    for(int i=0;i<leaf.size();i++){
        sum+=pow(1+r/100,Node[leaf[i]].layer-1)*Node[leaf[i]].data;
    }
    printf("%.1fn",sum*p);
    system("pause");
    return 0;
}