剑指offer---替换空格

题目：替换空格

要求：请实现一个函数，将一个字符串中的每个空格替换成“%20”。例如，当字符串为We Are Happy.则经过替换之后的字符串为We%20Are%20Happy。

class Solution {
public:
    void replaceSpace(char *str,int length) {

    }
};

解题代码：

class Solution {
public:
    void replaceSpace(char *str,int length) {
        if(str == nullptr || length <= 0)
            return ;

        int origLength = 0;
        int numBlank = 0;
        int i = 0;
        while(str[i] != ''){
            if(str[i] == ' ')
                numBlank++;
            origLength++;
            i++;
        }

        int newLength = origLength + 2 * numBlank;
        if(newLength > length)
            return ;

        int pOld = origLength;
        int pNew = newLength;
        while(pOld>=0 && pOld<pNew){
            if(str[pOld] != ' ')
                str[pNew--] = str[pOld];
            else{
                str[pNew--] = '0';
                str[pNew--] = '2';
                str[pNew--] = '%';
            }
            pOld--;
        }
    }
};