4-替换空格

/*
length为字符数组string的总容量
*/
void ReplaceBlank(char string[], int length){
    if(string==nullptr && length<=0)
        return;

    // originalLength 为字符串string的实际长度
    int originalLength = 0;
    int numberOfBlank = 0;
    int i = 0;
    while(string[i] != ‘\0‘){
        ++originalLength;
        if(string[i] == ‘ ‘)
            ++numberOfBlank;
        ++i;
    }

    // newLength 为把空格替换成‘%20‘之后的长度
    int newLength = originalLength + numberOfBlank*2;
    if(newLength > length)
        return;

    int indexOfOriginal = originalLength;
    int indexOfNew = newLength;
    while(indexOfOriginal >=0 && indexOfNew > indexOfOriginal){
        if(string[indexOfOriginal] == ‘ ‘){
            string[indexOfNew--] = ‘0‘;
            string[indexOfNew--] = ‘2‘;
            string[indexOfNew--] = ‘%‘;
        }else{
            string[indexOfNew--] = string[indexOfOriginal];
        }
        --indexOfOriginal;
    }    

}