Problem:
Score : 300 points

Problem Statement

You are given an integer N. Among the integers between 1 and N (inclusive), how many Shichi-Go-San numbers (literally "Seven-Five-Three numbers") are there?

Here, a Shichi-Go-San number is a positive integer that satisfies the following condition:

When the number is written in base ten, each of the digits 7, 5 and 3 appears at least once, and the other digits never appear.

Constraints

1 \leq N < 10^9

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the number of the Shichi-Go-San numbers between 1 and N (inclusive).

Sample Input 1

575

Sample Output 1

4

There are four Shichi-Go-San numbers not greater than 575: 357, 375, 537 and 573.

Sample Input 2

3600

Sample Output 2

13

There are 13 Shichi-Go-San numbers not greater than 3600: the above four numbers, 735, 753, 3357, 3375, 3537, 3557, 3573, 3575 and 3577.

Sample Input 3

999999999

Sample Output 3

26484

Solution in Rust (1.15.1) (judge verdict: Accepted)

use std::io::*;
use std::str::FromStr;
use std::collections::HashMap;
use std::collections::BTreeSet;
use std::cmp;
use std::num::Wrapping; // overflowを回避
use std::f64::consts;

fn main() {
    let n: i32 = read();
    let n_str: String = n.to_string();
    let min_len: usize = n_str.len();
    let input_vec: Vec<String> = vec!["7".to_string(), "5".to_string(), "3".to_string()];

    let mut out_vec: Vec<String> = vec![];

    for length in 3..min_len+1 {
        dfs(String::from(""), length, &mut out_vec, &input_vec);
    }

    let mut count = 0;

    for str in out_vec {
        if is_753(&str) && str.parse::<i32>().unwrap() <= n {
            count+=1;
        }
    }

    println!("{}", count);
}

fn is_753(s: &String)-> bool {
    if s.contains(&"7".to_string()) &&
        s.contains(&"5".to_string()) &&
        s.contains(&"3".to_string()) {
        return true;
    }
    return false;
}

fn dfs(mut s: String, min_len: usize, out_vec: &mut Vec<String>, input_vec: &Vec<String>) {
    if s.len() >= min_len {
        out_vec.push(s.clone());
        return;
    }

    for c in input_vec {
        dfs(s.clone() + c, min_len, out_vec, input_vec);
    }
}

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("failed to read char") as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().expect("failed to parse token")
}