【實驗7】流類庫和輸入輸出

時間 2019-11-17

標籤實驗7 輸入輸出简体版

原文原文鏈接

基礎練習：ios

（1）教材習題11-7函數

#include<iostream>
using namespace std;

int main(){
    ios_base::fmtflags original_flags = cout.flags();        //保存此格式化參數設置
    cout << 812 << '|';
    cout.setf(ios_base::left,ios_base::adjustfield);         //把對齊方式改爲左對齊
    cout.width(10);                                          //把寬度設置爲10
    cout << 813 << 815 << '\n';
    cout.unsetf(ios_base::uppercase|ios_base::scientific);   //改爲浮點數的顯示設置
    cout << 831.0;
    cout.flags(original_flags);                              //恢復保存的格式化參數設置
    return 0;
}

（2）教材習題11-3spa

#include<iostream> 
#include<fstream>
using namespace std;

int main(){
    ofstream filel("test.txt");
    filel << "已成功寫入文件！";
    filel.close();
    return 0;
}

（3）教材習題11-43d

#include<iostream>
#include<fstream>
using namespace std;
int main(){
    char s;
    ifstream in ("test.txt");
    if (!in) {
        cout  <<  "fail to open."  <<  endl;
        return 1;
    }
    in >> s;
    cout << s << endl;
    in.close() ;
    return 0;
}

應用練習：code

（1）blog

#include<iostream>
#include<fstream>
#include<string>
#include<stdlib.h>
#include<ctime> 
using namespace std;

struct student
{
    int num;
    string ID;
    string name;
    string clas;
}stu[100];

int main(){ 
    ifstream in ("list.txt");
    if (!in){
        cout << "fail to open." << endl;
        return 1;
    }
    int i = 0;
    while (in >> stu[i].num >> stu[i].ID >> stu[i].name >> stu[i].clas)
        i++; //統計有幾位同窗 
    in.close ();
    ofstream out ("roll.txt");       //存放被點的人 
    srand((unsigned)time(NULL));    //利用時間隨機 
    for ( int n = 1; n <= 5; n++ )  //隨機五位 
    {
        int a = 1 + rand() % ( i + 1 ) ;
        cout <<stu[a].num  << " "
             <<stu[a].ID   << " "
             <<stu[a].name << " "
             <<stu[a].clas << endl;
        out  <<stu[a].num  << " "
             <<stu[a].ID   << " "
             <<stu[a].name << " "
             <<stu[a].clas << endl;
    }
    out.close();
    return 0;
}

不知道爲何輸出的全是0……看了看好像好幾個同窗都這樣啊…求大佬解釋……ci

（2）string

#include<iostream>
#include<fstream>
using namespace std;

bool str(char a){   //判斷是不是字符
    if((a>='A'&&a<='z')||(a>='0'&&a<='9'))
        return true;
    else
        return false;
}

int main(){
    int str_number = 0;     //統計字符數
    int word_number = 0;    //統計單詞數
    int line_number = 1;    //統計行數
    ifstream in("data.txt");
    if(!in){
        cout << "fail to open." << endl;
        return 1;
    }
    while(in){
        char a;
        in.read(reinterpret_cast<char*>(&a),sizeof(a));
        if(str(a))
            str_number++;
        if(a==' '||a=='.'||a==','||a=='!'||a=='?'||a=='"'||a=='('||a==')'||a==':')
            word_number++;
        if(a=='\n')
            line_number++;
    }
    in.close();
    cout << "字符數：" << str_number << endl;
    cout << "單詞數：" << word_number << endl;
    cout << "行數：" << line_number << endl;
    return 0;
}