剑指offer 面试题4 替换空格

#include <stdio.h>
#include <string.h>
void blankToSymbol(char a[]);
int main(int argc, char *argv[])
{
/*测试用例：a)功能测试； b,c,d,e，f)特殊值（空格在开头，在结尾， 连续两个空格,全空格,没空格）；g)负面测试 （空字符串）*/
char a[80] = "we are happy";
char b[80] = " we are happy";
char c[80] = "we are happy ";
char d[80] = "we  are happy";
char e[80] = "   ";
char f[80] = "weare";
char *g = NULL;

blankToSymbol(a);
blankToSymbol(b);
blankToSymbol(c);
blankToSymbol(d);
blankToSymbol(e);
blankToSymbol(f);
blankToSymbol(g);

return 0;

}

void blankToSymbol(char a[]){//长度不用给 ，自己求
if(a == NULL) {//增强鲁棒性
printf("blank to symbol failed!\n");
return;
}
int i, j;
int cntZero = 0;
int length = 0;//字符串长度，不算\0
for(i=0 ; a[i]!='\0' ; i++){
length++;
if(a[i] == ' '){
cntZero++;
}
}

for(i=length, j = length+cntZero*2 ; i>=0,j>=0 ; i--, j--){//计算公式别写错 ,i取到length，即\0
if(a[i] != ' '){
a[j] = a[i];
}
else{
a[j--] = '0';
a[j--] = '2';
a[j] = '%';
}
}
printf("%d\n%s\n", strlen(a), a);
}