Problem E: One Stroke----暴力

Problem E: One Stroke

Time Limit: 2 Sec  Memory Limit: 1280 MB
Submit: 238  Solved: 44
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Description

    There is a complete binary tree which includes n nodes. Each node on the tree has a weight w, each edge on the tree is directed from the parent node to the child node. Give you a pen, draw from the any node along the directed edge at one stroke. It is required that the sum of those drawn nodes’ s weight is no more than k. How many node can be drawn at most in one stroke? 

Input

    The first line input an positive integer T(1<=T<=10)indicates the number of test cases. Next, each case occupies two lines. The first line input two positive integers n(1<=n<=10^6) and k,(1<=k<=10^9)

    The second line input n integers w(1<=w <=10^3),, indicate the weight of nodes from the first level of the tree and from left to right. 

Output

    For each test cases, output one line with the most number of nodes can be drawn in one stroke. If any node likes this doesn’t exists, output -1. 

Sample Input

15 6 2 3 4 1 7

Sample Output

3

题目链接：http://acm.hzau.edu.cn/problem.php?cid=1029&pid=4

题目的意思就是说有一棵二叉树，问你点权之和不超过k的最长路径长度是多少。

暴力就好，从下往上

代码：

#include <cstdio>#include <cstring>#include <iostream>using namespace std;int n,k;int a[1000010];int solve(int x){    int x1=x;    int len=0;    while(x1>-1){        if(a[x]-a[x1]>k){            break;        }        len++;        if(x1==0)            break;        x1>>=1;    }    return len-1;}int main(){    int t;    scanf("%d",&t);    while(t--){        scanf("%d%d",&n,&k);        for(int i=1;i<=n;i++){            scanf("%d",&a[i]);            a[i]+=a[i/2];        }        int ans=0;        for(int i=n;i>=1;i--){            ans=max(ans,solve(i));        }        if(ans)            printf("%d\n",ans);        else            printf("-1\n");    }}