实验7

4. 实验任务4

task4.c源码:

#define  _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>

int main() {
    FILE* fp;
    char ch;
    int cnt = 0;

    fp = fopen("data4.txt", "r");
    if (fp == NULL) {
        printf("fail to open the file\n");
        exit(0);
    }

    while (!(feof(fp))) {
        ch = fgetc(fp);
        if (ch == ' ' || ch == '\n') continue;
        if (ch == EOF) break;
        cnt++;
    }
    fclose(fp);

    printf("data4.txt中有字符%d个\n", cnt);

    return 0;
}

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5. 实验任务5

task5.c

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6. 实验任务6

源代码

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<time.h>

#define N 80
#define M 5

typedef struct{
    long number;
    char name[20];
    char classname[20];
}STU;

void finput(STU stu[],int n);//从list.txt读入
void foutput(STU stu[],STU lucky[],int m);//取随机数，并写入lucky.txt
void output(STU lucky[],int n);//屏幕上输出

int main(){
    STU stu[N],lucky[5];

    finput(stu,N);

    foutput(stu,lucky,M);

    output(lucky,M);

    return 0;
}

void finput(STU stu[],int n){
    FILE *fp;
    int i;

    fp = fopen("list.txt","r");
    if(fp==NULL){
        printf("fail\n");
        exit(0);
    }

    while(!feof(fp))
        for(i=0;i<N;++i)
            fscanf(fp,"%d%s%s",&stu[i].number,stu[i].name,stu[i].classname);

    fclose(fp);
}

void foutput(STU stu[],STU lucky[],int m){
    FILE *fp;
    int i;

    fp = fopen("lucky.txt", "w");
    if (fp==NULL) {
        printf("fail\n");
        exit(0);
    }

    srand(time(NULL));
    for(i=0;i<m;++i){
        int number=rand()%N;//在0,N-1间取随机整数
        lucky[i]=stu[number];
    }

    for(i=0;i<m;++i)
        fprintf(fp,"%d\t%s\t%s\n",lucky[i].number,lucky[i].name,lucky[i].classname);

    fclose(fp);
}

void output(STU lucky[],int n){
    int i;

    for(i=0;i<n;++i)
        printf("%d\t%s\t%s\n",lucky[i].number,lucky[i].name,lucky[i].classname);

}

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