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2018去哪网春招笔试

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2018去哪网春招笔试

2018去哪网春招笔试

原型题目：http://oj.leetcode.com/problems/word-ladder/

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#include <bits/stdc++.h>

using namespace std;

int main()
{
    freopen("in","r",stdin);

    string st,en,str;
    vector<string> arr;
    pair<string, int> now;
    queue<pair<string, int> > que;
    bool ans = false;
    cin>>st;

    en=st;
    reverse(en.begin(), en.end());//创建终点
    while(cin>>str)
        arr.push_back(str);
    arr.push_back(en);
    //for(auto it=arr.begin(); it!=arr.end(); it++)
    //    cout<<*it<<endl;
    que.emplace(st, 1);//将起点加入点集
    while(!que.empty())
    {
        //取出队列首部
        now = que.front();
        //cout<<now.first<<" "<<now.second<<endl;
        que.pop();
        if(now.first==en)
        {
            //找到终点，输出当前路径数
            cout << now.second << endl;
            return 0;
        }
        //超过最大转换次数继续寻找
        if(now.second>99)
            continue;
        //遍历arr查找
        for(auto it=arr.begin(); it!=arr.end(); it++)
        {
            //比较当前路径与下一路径的字符是否只差1，差1加入队列
            string tmp=now.first,tmp2=*it;
            int sum=0,len=tmp.length();
            for(int i=0;i<len;i++)
                if(tmp[i]!=tmp2[i])
                    sum++;
            if (sum == 1)
                que.emplace(*it, now.second + 1);
        }
    }
    cout<<"0"<<endl;
    return 0;
}

DFS+剪枝

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#include <iostream>
#include <cstring>
#define maxn 100000
int a[maxn],b[1010],n,m,ans,siz;
using namespace std;

void dfs(int j,int siz)
{
    if(siz>ans)
        ans=siz;
    if(j==-1)
        return ;
    for(int i=j;i>=0;i--){
        if(siz+a[i]<=m&&siz+b[i]>ans){
            dfs(i-1,siz+a[i]);
        }
    }
}

int main()
{
    cin>>n>>m;
    cin>>a[0];
    b[0]=a[0];
    for(int i=1;i<n;++i){
        cin>>a[i];
        b[i]=b[i-1]+a[i];
    }
    ans=0;
    dfs(n-1,0);
    if(ans==m)
        cout<<"perfect"<<endl;
    else
        cout<<"good"<<endl;
    return 0;
}

01背包只过80%

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#include <iostream>
#include <cstring>
#define maxn 100000
int a[maxn],dp[maxn];;
using namespace std;
int main()
{
    int n,m,ans=0;
    cin>>n>>m;
    memset(dp,0,sizeof(dp));
    for(int i=1;i<=n;i++)
    {
        cin>>a[i];
        ans+=a[i];
    }

    dp[0]=1;
    for(int i=1;i<n;i++)
    {
        for(int j=m;j>=a[i];j--)
        {
            if(j>=a[i])
                dp[j]+=dp[j-a[i]];
        }
    }

    if(dp[m]>0''ans==m)
        cout<<"perfect"<<endl;
    else
        cout<<"good"<<endl;

    return 0;
}