把字符串中的空格替换成%20

#include<iostream>
using namespace std;

void ChangeSpace(char* buf,int len)
{
    if(buf == NULL || len <= 0) return ;
    
    int count = 0;
    for(int i=0;i<len;i++)
    {
        if(buf[i] == ' ')
            count ++;
    }

    for(int i=len-1;i>=0;i--)
    {
        if(buf[i] != ' ')
            buf[i+2*count] = buf[i];
        else 
        {
            count --;
            buf[i+2*count] = '%';
            buf[i+2*count+1] = '2';
            buf[i+2*count+2] = '0';
        }
    }

    return ;
}

int main()
{
    char buf[64] = {0};
    strcpy(buf,"We Are Happy");
    ChangeSpace(buf,sizeof(buf));
    for(int i=0;i<sizeof(buf);i++)
    {
        cout << buf[i];
    }

    system("pause");
    return 0;
}