第三次实验的内容哒。
运行环境visual studio 2019
如果需要在别的环境中运行请将诸如scanf后面的_s去掉,还有加上#include<string.h>和#include<stdlib.h>,因为vs里面的iostream头文件里默认包含了这些文件,而别的环境没有。
可能写得不一定很好,但起码都是能用的QAQ。
如果发现错误请及时留言呐,觉得不错的话扫一下下面的二维码(点一下赏字会出现哒),资助哪怕一点点也是极好哒。
PS:不然只能吃土了。服务器维护也是要花钱的啊。

1.

//从左到右计算表达式(无视运算符优先级)
//date:29/10/2019
//code by kohaku
//All rights reserved.

#include<stdio.h>
#include <iostream>

int main()
{
    double a = 0;
    double out = 0;
    double in = 0;
    char op = '\0';
    printf("Enter an epression:");
    scanf_s("%lf", &out);           //输入第一个数字
    //将一个运算符和一个数字视为一组,循环计算
    while (1) {
        op = getchar();             //输入运算符或者接受回车
        if (op == '\n')break;       //若用户回车则结束输入
        scanf_s("%lf", &in);
        if (op == 43)out += in;     //判断运算符类型并计算
        if (op == 45)out -= in;
        if (op == 42)out *= in;
        if (op == 47)out /= in;
    }
    printf("Value of expression:");
    printf("%lf", out);
}

2.

//使用牛顿法计算平方根
//date:29/10/2019
//code by kohaku
//All rights reserved.
#include<stdio.h>
#include<math.h>
#include <iostream>

int main()
{
    double number = 0;
    double out = 1;
    double avg=0;

    printf("Enter a positive number:");
    scanf_s("%lf", &number);

    while (1) {
        avg = (out + number / out) / 2;
        if (fabs(avg - out) <= 0.00001 * out)break;
        out = avg;
    }

    printf("Square root:%lf", out);

}

3.

//逆向输出句子
//date:25/10/2019
//code by kohaku   
//All rights reserved.

#include<stdio.h>
#include <iostream>

int main()
{
    char str[1000];
    char end;
    int i = 0;
    char* p;
    printf("Enter a sentence:");
    //读取句子,将所以空格处理为\0,遇到结束符停止
    while (1) {
        str[i] = getchar();
        if (str[i] == 32)str[i] = '\0';
        if (str[i] == 33 || str[i] == 63 || str[i] == 46)break;
        i++;
    }
    printf("Reversal of sentence:");
    //存储结束符,将结束符变为\0
    end=str[i];
    str[i] = '\0';
    //向前搜索,遇到\0时,将指针移动到下一格,以字符串输出
    for (int n=i-1; n >= 0; n--) {
        if (str[n] =='\0') {
            p = &str[n+1];
            printf("%s ", p);
        }
    }
    //输出第一个单词
    printf("%s", str);
    printf("%c", end);
}

4.

//这是一个凯撒加密算法
//date:25/10/2019
//code by kohaku   
//All rights reserved.

#include<stdio.h>
#include <iostream>

int main()
{
    char str[80] = { 0 };
    int num = 0;
    int i = 0;
    int move = 0;
    printf("Enter message to be encrypted:");
    //逐个读取字符并计数,遇到结束符停止
    while (1) {
        str[i] = getchar();
        if (str[i] == 33 || str[i] == 63 || str[i] == 46)break;
        i++;
    }
    //最后添加一个终止符
    str[i+1] = '\0';
    printf("Enter shift amount(1-25):");
    scanf_s("%d", &move);
    //加密过程
    for (int n = 0; n < i; n++) {
        if (str[n]==32||str[n]==44)continue;
        else if (str[n] >= 97)str[n] = ((str[n] - 'a') + move) % 26 + 'a';
        else str[n] = ((str[n] - 'A') + move) % 26 + 'A';
    }
    printf("Encrypted message:%s", str);
}


5.

//数字字符串转化为整数
//date:29/10/2019
//code by kohaku
//All rights reserved.
#include<stdio.h>
#include <iostream>
#include<string>
#include<math.h>
int main()
{
    char in[20] = { '\0' };
    int len = 0;
    long long out = 0;
    gets_s(in);
    len = strlen(in);
    //循环计算每一位的值(使用ascii码减去'0'的值),乘上对于位数的10的幂
    for (int i = 0; i < len; i++) {
        out += pow(10, len - i-1) * ((int)in[i] - 48);
    }
    printf("%lld", out);
}

吾辈名为秋月琥珀,今后也请多多关照了