一波C语言字符数组实用技巧集锦

字符数组倒序

#include  

 void daoxu(char str[]){ 
   int i; 
   char temp; 
   for(i = 0; i < strlen(str) / 2 ; i ++){ 
     temp = str[i]; 
     str[i] = str[strlen(str) - i-1]; 
     str[strlen(str) - i-1] = temp; 
   } 
 } 

单词计数   

 int wordCount(char str[]){ 
   int i; 
   int count = 0; 
   int word = 0; 
   for (i = 0 ; str[i] != '' ; i ++) 
   { 
     if (str[i] == ' ') 
     { 
word = 0; 
     }else if (word == 0) 
     { 
word = 1; 
count ++; 
     } 
   } 
   return count; 
 } 

字符大写转小写

 void mylwr(char str[]){ 
   int i; 
   for (i = 0 ; str[i] != '' ; i ++) 
   { 
     if (str[i] >= 'A' && str[i] <= 'Z') 
     { 
str[i] += 'a' - 'A'; 
     } 
   } 
 } 

字符小写转大写

 void myupr(char str[]){ 
   int i; 
   for (i = 0 ; str[i] != '' ; i ++) 
   { 
     if (str[i] >= 'a' && str[i] <= 'z') 
     { 
str[i] -= 'a' - 'A'; 
     } 
   } 
 } 

字符数组计算字符串长度   

 int mylen(char str[]){ 
   int len; 
   for (len = 0 ; str[len] != '' ; len ++); 
   return len; 
 } 

字符串连接 

 void mycat(char str1[],char str2[]){ 
   int i,j; 
   for (i = 0 ; str1[i] != '' ;i++); 
   for (j = 0 ; str2[j] != '' ; j ++) 
   { 
     str1[i + j] = str2[j]; 
   } 
   str1[i + j] = ''; 
 } 

指定长度串接 

void myncat(char str1[],char str2[], int len){ 
   int i,j; 
   for(i = 0; str1[i] != ''; i++); 
   for (j = 0; j < len; j++) 
   { 
     str1[i + j] = str2[j]; 
   } 
   str1[i + j] = ''; 
 } 

字符数组拷贝     

 void mycpy(char dst[],char src[]){ 
   int i = 0; 
   do  
   { 
     dst[i] = src[i]; 
   } while (src[i++] != ''); 
 } 

字符数组指定长度拷贝     

 void myncpy(char dst[],char src[], int len){ 
   int i; 
   for (i = 0; i < len; i++) 
   { 
     dst[i] = src[i]; 
   } 
   dst[i] = ''; 
 } 

找出句子中最长的单词 

 void longest(char dst[],char src[]){ 
   int i = 0,j; 
   int count =0; 
   int max = -1; 
   do  
   { 
     if (src[i] ==' ' || src[i] == '') 
     { 
if (count > max) 
{ 
  max = count; 
  for (j = 0; j < count; j++) 
  { 
    dst[j] = src[i - count + j]; 
  } 
  dst[j] = ''; 
} 
count = 0; 
     }else{ 
count++; 
     } 
   } while (src[i++] != ''); 
 } 

从字符串中提取整形数字

#include  
 
int getint(char str[], int a[]){//从字符串中提取数字并放在数组中 
  int i = 0; 
  int w = 0; 
  int c = 0; 
  int j, k; 
  do  
  { 
    if (str[i] > '0' && str[i] <= '9') 
    { 
      w++; 
    }else if (w) 
    { 
      j = 0; 
      for (k = w; k > 0; k--) 
      { 
 j *= 10; 
 j += str[i - k] - '0'; 
      } 
      w = 0; 
      a[c] = j; 
      c++; 
    } 
  } while (str[i++] != ''); 
  return c; 
} 
 
void main(){ 
  char str[100]; 
  int a[100]; 
  int i, j; 
  gets(str); 
  i = getint(str,a); 
  for (j = 0; j < i; j++) 
  { 
    printf("%d ",a[j]); 
  } 
} 

整形、字符数组型转换

#include  
#include  
 
int sumof1(int x)//求一个数转换成二进制以后1的个数 
{ 
  int countx = 0; 
  while(x) 
  { 
    countx ++; 
    x &= x-1; //每位与一次x - 1；就能消掉最后一个1 
  } 
  return countx; 
} 
 
void main(){ 
 
  char c[10]; 
  int i = 999; 
 
  itoa(i, c, 10);//以10进制转换成字符数组 
  puts(c); 
 
  itoa(i, c, 16);//以16进制转换成字符数组 
  printf("0x%sn", c); 
 
  itoa(i, c, 8);//以8进制转换成字符数组 
  printf("0%sn", c); 
 
  itoa(i, c, 2);//以2进制转换成字符数组 
  puts(c); 
 
  i = atoi(c);//再将字符串转成整形 
  printf("%dn", i); 
 
  printf("%dn", sumof1(i));//以2进制表示时1的个数 
}