统计一行字符串中有多少个单词

【题目】输入一行字符,统计其中有多少个单词,每两个单词之间以空格隔开。如输入: This is a c++ program. 输出：5
较简单就不做注释了

#include 
using namespace std;

int CountWord(char * str)
{
    if (' ' == *str)
    {
        str++;
    }
    int flag = false;
    int num = 0;
    while(*str != '\0')
    {
        if (' ' != *str)
        {
            if (!flag)
            {
                flag = true;
                num++;
            }
        }
        else
        {
            flag = false;
        }
        str++;
    }
    return num;
}

int main()
{
    char s[100] = "  I am a  student  2 school";
    cout << CountWord(s) << endl;
    return 0;
}