用字符替换字符串中的空格

#include <iostream>
#include<cstring>

using namespace std;
class Solution {
public:
    void replaceSpace(char *str,int length) {

        if(str==NULL) return;
        int count=0;
        for(int i=0;i<length;++i)
        {
            if(str[i]==' ')
            {
                ++count;

            }
        }

        int space=count*2;//表示需要挪动多少个空位
        for(int i=length-1;i>=0;--i)
        {
                if(str[i]!=' ')
                {
                    str[i+space]=str[i];
                }

                else
                {

                    str[i+space]='0';
                    str[i+space-1]='2';
                    str[i+space-2]='%';
                    space-=2;

                }
        }

    }
};
int main()
{

    char str[]="We Are Happy";
    int length=strlen(str);
    cout<<str<<endl;
    Solution s;
    s.replaceSpace(str,length);
    cout<<str<<endl;
    return 0;
}