c和指针阅读笔记

#include <stdio.h>

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void main()

{

int x;

int i;

scanf("%d",&x);

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for(i = 0; i <x;i++)

{

printf("\n");

}

}

#include <math.h>

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const double DIFF = 0.00001;

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int main(int argc, char* argv[])

{

????float n, s,s0;

????s = 1;

????s0 = 0;

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????scanf("%f", &n);

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????while (fabs((double)(s - s0)) >= DIFF)

????{

????????s0 = s;

????????s = (s + n / s) / 2;

????????printf(" %f ", s);

????}

????printf("\n Result: %f ", s);

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????return 0;

}

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#define _CRT_SECURE_NO_WARNINGS

#include <stdio.h>

#include <math.h>

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void main()

{

????int n = 2;

????int i = 0;

????int flag = 0;

????int num = 1;

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????printf(" 2 ");

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????while (n <= 100)

????{

????????for (i = 2; i < (sqrt(n)+1);i++)

????????{

????????????if ((n%i) == 0)

????????????{

????????????????flag = 1;

????????????????break;

????????????}

????????}

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????????if (flag == 0)

????????{

????????????printf(" %d ", n);

????????????num++;

????????}

????????????

????????n++;

????????flag = 0;

????}

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????printf("num :\n",num);

}

#define _CRT_SECURE_NO_WARNINGS

#include <stdio.h>

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void main()

{

????int a, b, c;

????scanf("%d,%d,%d", &a, &b, &c);

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????if ((a >= (b + c)) || (b >= (c + a)) || (c >= (a + b)))

????????printf(" Input Error");

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????if (a == b)

????{

????????if (a != c)

????????????printf("Isosceles triangle");

????????else

????????????printf("An equilateral triangle");

????}

????else

????{

????????if (a == c)

????????{

????????????if (a != b)

????????????????printf("Isosceles triangle");

????????????else

????????????????printf("An equilateral triangle");

????????}

????????else

????????{

????????????if (b == c)

????????????{

????????????????if (a != b)

????????????????????printf("Isosceles triangle");

????????????????else

????????????????????printf("An equilateral triangle");

????????????}

????????????else

????????????????printf("triangle");

????????}

????}

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????printf("\n the end \n");

}

void My_strcpy(char dst[], const char str[],const int number)

{

????int srclength = strlen(str);

????int i = 0;

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????if (srclength <= number)

????{

????????strcpy(dst, str);

????????for (i = srclength; i < number;i++)

????????{

????????????dst[i] = ‘\0‘;

????????}

????}

????else

????{

????????for (i = 0; i < number;i++)

????????{

????????????dst[i] = str[i];

????????}

????}

}

#define _CRT_SECURE_NO_WARNINGS

#include <stdio.h>

#include <string.h>

#include <stdlib.h>

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const int MAX_NUM = 128;

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void main()

{

????char buff[MAX_NUM];

????char buff2[MAX_NUM];

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????while (gets_s(buff, MAX_NUM) != NULL)

????{

????????if (strcmp(buff, buff2) != 0)

????????????puts(buff);

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????????strcpy(buff2, buff);

????}

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????printf("========");

}

int substr(char dst[], const char src[], const int offset, const int len)

{

????int srclength = strlen(src);

????int i,reallength,j;

????if ((srclength < offset) || (offset <0) ||(len <0))

????????return 0;

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????reallength = ((offset + len) > srclength) ? srclength : (offset + len);

????for (i = offset; i < reallength;i++)

????????dst[i-offset] = src[i];

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????j = reallength - offset;

????dst[i] = ‘\0‘;

????return j;

}

void debblank(char string[])

{

????int length = strlen(string);

????int i, j, flag;

????flag = 0;

????/*遍历数组*/

????for (i = 0; i <(length-1);i++)

????{

????????/*防止数组越界，将长度-1 ，判断当前数组值与下一个值都是空格，则i存入下一数组下表，flag标志置1*/

????????if ((string[i] == ‘ ‘) && (string[i + 1] == ‘ ‘))

????????{

????????????flag = 1;

????????????i++;

????????}

????????????

????????/*如果flag标志位1 说明连续两个空格存在，且下标标志位在第二个空格*/

????????if (flag == 1)

????????{

????????????/*移动数组，覆盖第一个空格*/

????????????for (j = i; j < (length-1) ;j++)

????????????????string[j-1] = string[j];

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????????????/*确保数组最后一位被移动*/

????????????string[j] = string[length];

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????????????/*覆盖后长度-1*/

????????????length--;

????????}

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????????/*如果移动过数组，光标跳入下一数组下标，且当前还是空格，则回退至上一层，否则回档当前位置*/

????????if (flag == 1)

????????{

????????????if (string[i] == ‘ ‘)

????????????{

????????????????/*-2 是由于 for循环含有-1 */

????????????????i = i - 2;

????????????}

????????????else

????????????{

????????????????

????????????????flag = 0;

????????????????i--;

????????????}

????????}

????}

}