1.strcat()、strncat()字符串追加函数

#define _CRT_SECURE_NO_WARNINGS#include<stdio.h>#include<stdlib.h>#include<math.h>#include<string.h>int main0201()//字符串追加函数，注意字符串1有足够空间容纳字符串2{	char a[100] = "abc";	char b[100] = "defg";	strcat(a, b);//将字符串b追加到a之后，并输出a	printf("%s\n", a);	return 0;}int main0202(){	char a[100] = "abc";	char b[100] = "defg";	strncat(a, b,1);//将字符串b追加到a之后，并输出a	printf("%s\n", a);	return 0;}

2.strcmp()、strncmp()字符串比较函数

#include<stdio.h>int main0301()//字符串比较{	char a[100] = "abc";	char b[100] = "abcd";	if (strcmp(a, b)==0)//比较a，b是否相同		printf("相同");	else		printf("不同");	return 0;}int main0302()//字符串有限比较{	char a[100] = "abc";	char b[100] = "abcd";	if (strncmp(a, b,4) == 0)//比较a，b的前n个字符是否相同		printf("相同");	else		printf("不同");	return 0;}

3.strcpy()字符串拷贝函数

#include<stdio.h>int main0401()//字符串拷贝，将b拷贝到a中并覆盖a内容{    char a[100] = "abc";    char b[100] = "12345";    strcpy(a, b);    printf("%s\n", a);    return 0;}int main0402(){    char a[100] = "abc";    char b[100] = "12345";    strncpy(a, b,sizeof(a)-1);//将a字符串放满    printf("%s\n", a);    return 0;}

4.sprintf()格式化输入到字符串函数

#include<stdio.h>int main0501(){	char a[100];	sprintf(a, "%s", "hello world");	printf("%s\n", a);	return 0;}

5.sscanf()字符串读取函数

#define _CRT_SECURE_NO_WARNINGS#include<stdio.h>#include<stdlib.h>#include<math.h>#include<string.h>int main0601(){	char a[100] = "10+10";	int b;	int c;	sscanf(a, "%d+%d", &b, &c);	printf("%d+%d=%d\n", b, c, b + c);}int main0602(){	char a[100] = "43*25=";	int i, j;	char c;	sscanf(a, "%d%c%d=", &i, &c, &j);	int res=0;	switch (c)	{	case'+':		res = i + j;		break;	case'-':		res = i - j;		break;	case'*':		res = i * j;		break;	case'/':		res = i / j;		break;	default:		res = 0;	}	printf("%d%c%d=%d", i, c, j, res);}

6.strchr()字符查找函数

#include<stdio.h>#include<stdlib.h>int main0701(){	char a[100] = "hello world";	char* s;	s = strchr(a, 'l');	if(s!=NULL)	printf("%s\n", s);	return 0;}

7.strstr()字符串中查找子串

#include<stdio.h>#include<stdlib.h>int main0801()//字符串中查找子串{	char a[100] = "hello world";	char *s;	s = strstr(a, "llo");	printf("%s\n", s);	return 0;}

8.strtok()字符串分割函数

#define _CRT_SECURE_NO_WARNINGS#include<stdio.h>#include<stdlib.h>#include<math.h>#include<string.h>int main0901(){	char a[100] = "abc_bce_123_456";	char* s;	s = strtok(a, "_");	printf("%s\n", s);	s = strtok(NULL, "_");//第二次调用时，参数写NULL	printf("%s\n", s);	s = strtok(NULL, "_");	printf("%s\n", s);	return 0;}int main0902(){	char a[100] = "abc_bce_123_456";	char* s;	s = strtok(a, "_");	while (s)	{		printf("%s\n", s);		s = strtok(NULL, "_");	}	return 0;}

9.atoi函数

#include<stdio.h>#include<stdlib.h>int main10_01()//atoi(){	char a[] = "123";//将字符串转化为整数 atoi()	char b[] = "456";	int i = atoi(a) + atoi(b);	printf("%d\n", i);	return 0;}

10.atof函数

#include<stdio.h>#include<stdlib.h>  int main10_02()//atof{	char a[100] = "3.555";	double f = atof(a);	printf("%f\n", f);	return 0;}

11.将一个数字追加到字符串之后

#include<stdio.h>#include<stdlib.h>int main10_03()//将100追加到abc之后{	char a[100] = "222";	char str1[100] = "abc";	int num = 100;	sprintf(a, "%d", num);	strcat(str1, a);	printf("%s\n", str1);	return 0;}

12.将字符串中的值求出

#define _CRT_SECURE_NO_WARNINGS#include<stdio.h>#include<stdlib.h>#include<math.h>#include<string.h>int main011(){	char a[100] = "15+20=;22-11=;13*50=;70/20=";	char b[100] = {0};	char* p = strtok(a, ";");	while (p)	{		int i, j;		char c;		int sum = 0;		sscanf(p, "%d%c%d=", &i, &c, &j);		switch (c)		{		case '+':			sum = i + j;			break;		case '-':			sum = i - j;			break;		case '*':			sum = i * j;			break;		case '/':			sum = i / j;			break;		default:			sum = NULL;			break;		}		char temp[10] = {0};		sprintf(temp, "%s%d;", p ,sum);		strcat(b, temp);		p = strtok(NULL, ";");	}	strcpy(a, b);	printf("%s\n", a);	return 0;}

13.z自定义函数的调用和使用

#define _CRT_SECURE_NO_WARNINGS#include<stdio.h>#include<stdlib.h>#include<math.h>#include<string.h>int add(int a, int b)//自定义函数 {	return a + b;}void test()//定义一个自定义函数，没有返回值也没有参数 {	printf("test\n");} void test1();//声明需调用的函数void test2(int a);int mmax(int a, int b){	return (a > b) ? a : b;}int main012(){	int i = 2;	int j = 3;	int c = add(i, j);//调用函数	printf("%d\n", c);	test();//调用一个没参数，没返回值的函数	test1();	test2(i);//i是实参,实参可以是变量、常量也可以是表达式	int k=mmax(i, j);	printf("%d\n", k);	return 0;}void test1(){	printf("test1\n");}void test2(int a)//其中a为形参{	printf("a=%d\n", a);}

14.递归函数

#define _CRT_SECURE_NO_WARNINGS#include<stdio.h>void test3(int n){	if (n < 10)	{		test3(n + 1);	}	printf("n=%d\n", n);}int main14_01(){	int a = 0;	test3(a);	return 0;}

#define _CRT_SECURE_NO_WARNINGS#include<stdio.h>int age(int n)//n个人，后面的人比前面的人大2岁，求第n个人多大，第一个10岁{	if (n == 1)//递归结束条件		return 10;	return age(n - 1) + 2;}int main14_02(){	int a = 5;	printf("%d\n", age(a));	return 0;}

#define _CRT_SECURE_NO_WARNINGS#include<stdio.h>void to_bin(unsigned int n)//将一个十进制数转换为二进制{	int i = n % 2;	if (n >= 2)	{		to_bin(n / 2);	}	printf("%d\n", i);}int main14_03(){	int a = 13;	scanf("%d", &a);	to_bin(a);	return 0;}

#define _CRT_SECURE_NO_WARNINGS#include<stdio.h>char hex_char(unsigned int n)//将十进制数转换为16进制{	switch (n)	{	case 1:		return '1';	case 2:		return '2';	case 3:		return '3';	case 4:		return '4';	case 5:		return '5';	case 6:		return '6';	case 7:		return '7';	case 8:		return '8';	case 9:		return '9';	case 10:		return 'a';	case 11:		return 'b';	case 12:		return 'c';	case 13:		return 'd';	case 14:		return 'e';	case 15:		return 'f';	}	return '0';}void to_hex(unsigned int n){	int i = n % 16;	if (n >= 16)		to_hex(n / 16);	printf("%c", hex_char(i));}int main14_04(){	int a;	scanf("%d", &a);	to_hex(a);	printf("\n");	return 0;}

#define _CRT_SECURE_NO_WARNINGS#include<stdio.h>int fib(int n)////斐波那契数列 0,1,1,2,3,5,8,13,21,34,55{	if (n == 1)		return 1;	if (n == 2)		return 2;	return fib(n - 1) + fib(n - 2);}int main(){	int i;	for (i = 1; i < 20; i++)	{		printf("%d\n", fib(i));	}	return 0;}