Work_3

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

int main(){    
        int len = 10;
    int a[10], b[10];
    int temp;
    printf("请输入两个数组的内容：\n");
    for (int i=0; i < len; i++){
        scanf("%d",&a[i]);
    }
    for (int i=0; i < len; i++){
        scanf("%d", &b[i]);
    }
    for (int i=0; i < len; i++){
        temp = a[i];
        a[i] = b[i];
        b[i] = temp;
    }
    printf("交换后的a数组为：");
    for (int i=0; i < len; i++){
        printf("%d ", a[i]);
    }
    printf("\n交换后的b数组为：");
    for (int i=0; i < len; i++){
        printf("%d ", b[i]);
    }
    printf("\n");
    system("pause");
    return 0;
}    
            

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

int main(){
    double sum = 0.0;
    int flag = 1;
    for (int i = 1; i < 100; i++){
        sum = sum + (flag * 1.0) / i;
        flag = flag * (-1);
    }
    printf("输出结果为：%f", sum);
    printf("\n");
    system("pause");
    return 0;
}    

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

int main(){
    int temp;
    int count = 0;
    for (int i = 1; i < 100; i++){
        temp = i;
        while (temp > 0){
            if (temp % 10 == 9){
                count++;
            }
            temp = temp / 10;
        }
    }
    printf("9出现的次数为：%d", count);        
    printf("\n");
    system("pause");
    return 0;
}