（自用随笔）PAT A1022（30分）qsort问题待解决

思路：定义一个结构体来存书，重点在格式化输入。本来不想用string的，但是发现char*还是麻烦，就用了string，最后结果也没有多慢，最后一个测试用例270ms，在没用map和set优化的情况下还可以了。。。

如果会熟练使用map和set，可以参考其他人的博客，有更快的算法。

做的时候遇到了几个坑，首先我一开始用的是qsort函数，但是对我这个结构体排序完之后，里面的string居然丢失数据了！用sort就没事了。如果有大佬懂的话，希望可以点拨一下~

第二个坑是fflush这个函数，这个不是c/c++标准里面的，最好不要用了。想吸收每行输入结束的回车符，还是用getchar()吧。

AC代码：

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <vector>
#include <string>
#include <sstream>
#include <string.h>
#include <algorithm>

using namespace std;

struct Book{
    int id;
    string title;
    string author;
    vector<string> keywords;
    string publisher;
    int year;
};
Book *book;

int N,M;
string *query;

bool cmp(Book _a,Book _b)
{
    //Book *a = (Book*)_a;
    //Book *b = (Book*)_b;
    return _a.id < _b.id;
}

void Sear(int x,int index)
{
    int booknum = 0;
    switch(x)
    {
    case 1:
        for(int r = 0;r<N;r++)
        {
            if(book[r].title == query[index])
            {
                printf("\n%07d",book[r].id);
                booknum++;
            }
        }
        break;
    case 2:
        for(int r = 0;r<N;r++)
        {
            if(book[r].author == query[index])
            {
                printf("\n%07d",book[r].id);
                booknum++;
            }
        }
        break;
    case 3:
        for(int r = 0;r<N;r++)
        {
            for(int g = 0;g<book[r].keywords.size();g++)
            {
                if(book[r].keywords[g] == query[index])
                {
                    printf("\n%07d",book[r].id);
                    booknum++;
                    break;
                }
            }

        }
        break;
    case 4:
        for(int r = 0;r<N;r++)
        {
            if(book[r].publisher == query[index])
            {
                printf("\n%07d",book[r].id);
                booknum++;
            }
        }
        break;
    case 5:
        for(int r = 0;r<N;r++)
        {
            if(book[r].year == atoi(query[index].c_str()))
            {
                printf("\n%07d",book[r].id);
                booknum++;
            }
        }
        break;
    }
    if(booknum == 0)
    {
        printf("\nNot Found");
    }
}

int main()
{
    scanf("%d",&N);
    book = new Book[N];
    char temp[80];
    string s;
    char c;
    for(int i = 0;i<N;i++)
    {
        scanf("%d",&book[i].id);
        //fflush(stdin);
        c = getchar();
        scanf("%[^\n]",temp);
        //fflush(stdin);
        c = getchar();
        book[i].title = temp;
        scanf("%[^\n]",temp);
        //fflush(stdin);
        c = getchar();
        book[i].author = temp;
        //cout<<book[i].author<<endl;
        scanf("%[^\n]",temp);
        //fflush(stdin);
        c = getchar();
        s = temp;
        stringstream ss(s);
        string x;
        while(ss>>x)
        {
            book[i].keywords.push_back(x);
            x = "";           //清空字符串x
        }
        //cout<<book[i].keywords[0]<<book[i].keywords[1];
        scanf("%[^\n]",temp);
        //fflush(stdin);
        c = getchar();
        book[i].publisher = temp;
        scanf("%d",&book[i].year);
    }
    //cout<<book[0].author<<endl<<book[1].author<<endl<<book[2].author<<endl;
    sort(book,book+N,cmp);
    //cout<<book[0].author<<endl<<book[1].author<<endl<<book[2].author<<endl;
    scanf("%d",&M);
    query = new string[M];
    int num;
    for(int j = 0;j<M;j++)
    {
        scanf("%d: ",&num);
        scanf("%[^\n]",temp);
        //fflush(stdin);
        c = getchar();
        query[j] = temp;
        cout<<num<<": "<<query[j];

        Sear(num,j);
        if(j!=M-1)
        {
            printf("\n");
        }
    }
    return 0;
}

 

下面这个是第一次写的代码，排序后输出author，发现出错了

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <vector>
#include <string>
#include <sstream>
#include <string.h>
#include <algorithm>

using namespace std;

struct Book{
    int id;
    string title;
    string author;
    vector<string> keywords;
    string publisher;
    int year;
};
Book *book;

int N,M;
string *query;

int cmp(const void* _a,const void* _b)
{
    Book *a = (Book*)_a;
    Book *b = (Book*)_b;
    return a->id > b->id;
}

void Sear(int x,int index)
{
    int booknum = 0;
    switch(x)
    {
    case 1:
        for(int r = 0;r<N;r++)
        {
            if(book[r].title == query[index])
            {
                printf("\n%07d",book[r].id);
                booknum++;
            }
        }
        break;
    case 2:
        for(int r = 0;r<N;r++)
        {
            if(book[r].author == query[index])
            {
                printf("\n%07d",book[r].id);
                booknum++;
            }
        }
        break;
    case 3:
        for(int r = 0;r<N;r++)
        {
            for(int g = 0;g<book[r].keywords.size();g++)
            {
                if(book[r].keywords[g] == query[index])
                {
                    printf("\n%07d",book[r].id);
                    booknum++;
                    break;
                }
            }

        }
        break;
    case 4:
        for(int r = 0;r<N;r++)
        {
            if(book[r].publisher == query[index])
            {
                printf("\n%07d",book[r].id);
                booknum++;
            }
        }
        break;
    case 5:
        for(int r = 0;r<N;r++)
        {
            if(book[r].year == atoi(query[index].c_str()))
            {
                printf("\n%07d",book[r].id);
                booknum++;
            }
        }
        break;
    }
    if(booknum == 0)
    {
        printf("\nNot Found");
    }
}

int main()
{
    scanf("%d",&N);
    book = new Book[N];
    char temp[80];
    string s;
    char c;
    for(int i = 0;i<N;i++)
    {
        scanf("%d",&book[i].id);
        //fflush(stdin);
        c = getchar();
        scanf("%[^\n]",temp);
        //fflush(stdin);
        c = getchar();
        book[i].title = temp;
        scanf("%[^\n]",temp);
        //fflush(stdin);
        c = getchar();
        book[i].author = temp;
        //cout<<book[i].author<<endl;
        scanf("%[^\n]",temp);
        //fflush(stdin);
        c = getchar();
        s = temp;
        stringstream ss(s);
        string x;
        while(ss>>x)
        {
            book[i].keywords.push_back(x);
            x = "";           //清空字符串x
        }
        //cout<<book[i].keywords[0]<<book[i].keywords[1];
        scanf("%[^\n]",temp);
        //fflush(stdin);
        c = getchar();
        book[i].publisher = temp;
        scanf("%d",&book[i].year);
    }
    //cout<<book[0].author<<endl<<book[1].author<<endl<<book[2].author<<endl;
    qsort(book,N,sizeof(Book),cmp);
    cout<<book[0].author<<endl<<book[1].author<<endl<<book[2].author<<endl;
    scanf("%d",&M);
    query = new string[M];
    int num;
    for(int j = 0;j<M;j++)
    {
        scanf("%d: ",&num);
        scanf("%[^\n]",temp);
        //fflush(stdin);
        c = getchar();
        query[j] = temp;
        cout<<num<<": "<<query[j];

        Sear(num,j);
        if(j!=M-1)
        {
            printf("\n");
        }
    }
    return 0;
}

测试数据：（Yue后面的Chen被吃了，并且没有正确按照id大小排序）