C语言程序设计教程（第三版）课后习题5.7 （C++代码）

#include<iostream>
using namespace std;
void f(int t)
{
	if (t > 0 && t < 10)
	{
		cout << t<<" ";
    }
	else
	{
		f(t / 10);
		cout <<t%10<< " ";
	}

}
int main()
{
	system("color 03");
	int n,sum=0,t,a,b,r,q,m;
	cin >> n;
	t = n;
	r = n;
	for (int i = 1; i <= t; i++)
	{
		a = n % 10;
		n = n / 10;
		sum = sum + 1;
		if (n < 10)break;
	}
	sum = sum + 1;
	cout << sum << endl;
	f(n);
	cout << endl;
	for (int i = 1; i <=r; i++)
	{
		q= t % 10;
		t= t / 10;
		cout << q;
		if (t<=0)break;
	}
	
	
}
在这个里面的递归函数怎么只能出个1啊，放在别的项目里却能正常输出1 2 3 4 5

c++新手建议看看这个，比较好理解awa
#include <iostream>
#include <cmath>
using namespace std;
int main(){
    int n;
    cin>>n;
    int k=n,a=0;
    while (k){
        k/=10;
        a++;
    }
    cout<<a<<endl;
    int b[a]={0};
    for (int i=0; i<a; i++){
        b[i]=n/pow(10,(a-i-1));
        n-=b[i]*pow(10,a-i-1);
        cout<<b[i]<<' ';
    }
    cout<<endl;
    for (int i=a-1; i>=0; i--)
        cout<<b[i];
    return 0;
}

#include<iostream>
#include<string>
using namespace std;
int main()
{
    string num;
    cin >> num;

	int len = num.length();
	cout << len << endl;
	
	for (int i = 0; i < len; i++) {
		cout << num[i] << " ";
	}
	cout << endl;

	string new_num;
	for (;len >= 0; len--) {
		new_num.append(1,num[len]);
	}
	cout << new_num << endl;
}
我这个结果没问题啊

判断数组长度是不是有问题，你写的是当n为0就输出位数，但是还有后面的数字没有判断，就比如100，你取整为0，那100是1位数？

#include <iostream>

using namespace std;
void figure(int n)
{
    int count=0;
    while(n!=0){n/=10;count++;}
    cout<<count<<endl;
}
void sep(int n)
{
    int a1,a2,a3,a4,a5;
    a1=n%10;
    a2=n/10%10;
    a3=n/100%10;
    a4=n/1000%10;
    a5=n/10000%10;
    cout<<a5<<a4<<a3<<a2<<a1<<endl;
}
void rev(int n)
{
    int a1,a2,a3,a4,a5;
    a1=n%10;
    a2=n/10%10;
    a3=n/100%10;
    a4=n/1000%10;
    a5=n/10000%10;
    cout<<a1<<a2<<a3<<a4<<a5<<endl;
}
int main()
{
    int x;
    cin>>x;
    figure(x);
    sep(x);
    rev(x);
    return 0;
}

#include<stdio.h>

int main()
{
	int x;
	int y;
	int num;
	scanf("%d", &x);
	int z = x;
	for(y=0;z!=0;y++){
		z=z / 10;	
	}printf("%d\n", y);

	int mask = 1;
	int v = x;
	int n = x;

	while (v > 9) {
		v = v / 10;
		mask = mask * 10;
	}
	do {
		int d = x / mask;
		printf("%d ", d);
		x = x % mask;
		mask=mask / 10;
	} while (x > 0);
	printf("\n");
	while (n > 0) {
		num=n%10;
		printf("%d", num);
		n=n / 10;
	}

	return 0;
}

为何不用函数（递归）？

#include<iostream>
#include <math.h>
using namespace std;
int main()
{
    int a, b, i,temp, t, j;
    cin >> a;
    t = a;
    for (i = 0; t != 0; i++)
    {
        t = t / 10;
    }
    cout << i << endl;
    for (temp=i; temp != 0; temp--)
    {
        b = pow(10, temp - 1);
        b = (a / b) % 10;
        printf("%d ", b);
    }
    putchar('\n');
    for (j = 0; j != i; j++)
    {
        b = pow(10, j);
        b = (a / b) % 10;
        printf("%d", b);
    }
    return 0;
}