七七……题解……

#include <bits/stdc++.h>
using namespace std;
int main(){
    int n,ans = 0;
    cin >> n;
    for(int i = 1234567;i <= n;i++){
        int a = i / 10000000,b = i / 1000000 % 10,c = i / 100000 % 10,d = i /10000 % 10,
            e = i / 1000 % 10,f = i / 100 % 10,g = i / 10 % 10,h = i % 10;//分出……每一位……
        
        if(a != b && a != c && a != d && a != e && a != f && a != g && a != h && 
            b != c && b != d && b != e && b != f && b != g && b != h && 
            c != d && c != e && c != f && c != g && c != h && 
            d != e && d != f && d != g && d != h && 
            e != f && e != g && e != h && 
            f != g && f != h && 
            g != h) ans++;//如果……每一位……都不一样……加一……
         //如果一样……重复的……那一位……加一
        //本来循环……会加一……只要……九……
        else if(g == f || g == e || g == d || g == c || g == b || g == a) i += 9;
        else if(f == e || f == d || f == c || f == b || f == a) i += 99;
        else if(e == d || e == c || e == b || e == a) i += 999;
        else if(d == c || d == b || d == a) i += 9999;
        else if(c == b || c == a) i += 99999;
        else if(b == a) i += 999999;
    }
    cout << ans;
}