Question

undeclared identifier错误，请帮忙修改，谢谢

#include <iostream.h>
# include <string.h>
int main()
{
int m;n;sum;N;M;sum1;sum2;sum3;
cout << "Please enter an M:";
cin >> m;
cout << "Please enter an N:";
cin >> n;
for(int i=1;i<=M;i++)
sum1=sum1*i;
for(int j=1;j<=N;j++)
sum2=sum2*j;
for(int k=1;k<(M-N);k++)
sum3=sum3*k;
sum=sum1/(sum2*sum3);
cout << sum;
return 0;
}

Answer 1

这行变量定义语句写错了
int m;n;sum;N;M;sum1;sum2;sum3;
变量定义语句中间不用分号，用逗号，改成这样
int m;n，sum，N，M，sum1，sum2，sum3;

Answer 2

int m,n,sum,N,M,sum1,sum2,sum3;/////注意
sum1=?//初始化 如sum1=1
for(int i=1;i<=M;i++)
sum1=sum1*i;
sum2=?//初始化
for(int j=1;j<=N;j++)
sum2=sum2*j;
sum3=?//初始化
for(int k=1;k<(M-N);k++)
sum3=sum3*k;