剑指offer 04_替换字符串中的空格

 #include <stdio.h>

 void ReplaceBlank(char string[],int length){
         if(string == NULL || length == 0){
                 return;
         }

         int originalLength = 0;//
         int blankCount = 0;

         while(string[originalLength] != '\0'){
                 if(string[originalLength] == ' '){
                         ++blankCount;
                 }
                 ++originalLength;
         }

         int newLength = originalLength + blankCount * 2;

         if(newLength > length){//not enough space
                 return;
         }

         int indexFirst = originalLength;
         int indexSecond = newLength;
         while(indexFirst>=0 && indexSecond>indexFirst){
                 if(string[indexFirst] == ' '){
                         string[indexSecond--] = '0';
                         string[indexSecond--] = '2';
                         string[indexSecond--] = '%';
                 }else{
                         string[indexSecond--] = string[indexFirst];
                 }
                 --indexFirst;
         }
 }

 int main(){
         char str[50] = "We are happy.";
         printf("str = %s\n",str);

         ReplaceBlank(str,50);
         printf("str = %s\n\n",str);

         char str1[50] = "Wearehappy.";
         printf("str1 = %s\n",str1);

         ReplaceBlank(str1,50);
         printf("str1 = %s\n\n",str1);

         char str2[50] = "   We are happy.";
         printf("str2 = %s\n",str2);

         ReplaceBlank(str2,50);
         printf("str2 = %s\n\n",str2);

         char str3[50] = "";
         printf("str3 = %s\n",str3);

         ReplaceBlank(str3,50);
         printf("str3 = %s\n\n",str3);

         return 0;
 }

结果

str = We are happy.
str = We%20are%20happy.

str1 = Wearehappy.
str1 = Wearehappy.

str2 =    We are happy.
str2 = %%%20We%20are%20happy.

str3 =
str3 =