给定范围[L，R] ，任务是从该范围中找到满足以下条件的数字：
- 数字中的所有数字都是唯一的。
- 所有数字均小于或等于5。
例子：
Input: L = 4, R = 13
Output: 5
4, 5, 10, 12 and 13 are the only
valid numbers in the range [4, 13].
Input: L = 100, R = 1000
Output: 100
方法：如果范围很小，问题似乎很简单，因为在这种情况下，可以迭代范围内的所有数字并检查它们是否有效。但是由于范围可能很大，因此可以观察到有效数字的所有数字都必须与范围[0，5]不同，这表明最大数字不能超过543210。
现在，无需检查每个数字，而是可以从先前生成的数字中生成系列中的下一个有效数字。这个想法类似于这里讨论的方法。
下面是上述方法的实现：
C++
// C++ implementation of the approach
#include
using namespace std;
// Maximum possible valid number
#define MAX 543210
// To store all the required number
// from the range [1, MAX]
vector ans;
// Function that returns true if x
// satisfies the given conditions
bool isValidNum(string x)
{
// To store the digits of x
map mp;
for (int i = 0; i < x.length(); i++) {
// If current digit appears more than once
if (mp.find(x[i] - '0') != mp.end()) {
return false;
}
// If current digit is greater than 5
else if (x[i] - '0' > 5) {
return false;
}
// Put the digit in the map
else {
mp[x[i] - '0'] = 1;
}
}
return true;
}
// Function to generate all the required
// numbers in the range [1, MAX]
void generate()
{
// Insert first 5 valid numbers
queue q;
q.push("1");
q.push("2");
q.push("3");
q.push("4");
q.push("5");
bool flag = true;
// Inserting 0 externally because 0 cannot
// be the leading digit in any number
ans.push_back("0");
while (!q.empty()) {
string x = q.front();
q.pop();
// If x satisfies the given conditions
if (isValidNum(x)) {
ans.push_back(x);
}
// Cannot append anymore digit as
// adding a digit will repeat one of
// the already present digits
if (x.length() == 6)
continue;
// Append all the valid digits one by
// one and push the new generated
// number to the queue
for (int i = 0; i <= 5; i++) {
string z = to_string(i);
// Append the digit
string temp = x + z;
// Push the newly generated
// number to the queue
q.push(temp);
}
}
}
// Function to copmpare two strings
// which represent a numerical value
bool comp(string a, string b)
{
if (a.size() == b.size())
return a < b;
else
return a.size() < b.size();
}
// Function to return the count of
// valid numbers in the range [l, r]
int findcount(string l, string r)
{
// Generate all the valid numbers
// in the range [1, MAX]
generate();
// To store the count of numbers
// in the range [l, r]
int count = 0;
// For every valid number in
// the range [1, MAX]
for (int i = 0; i < ans.size(); i++) {
string a = ans[i];
// If current number is within
// the required range
if (comp(l, a) && comp(a, r)) {
count++;
}
// If number is equal to either l or r
else if (a == l || a == r) {
count++;
}
}
return count;
}
// Driver code
int main()
{
string l = "1", r = "1000";
cout << findcount(l, r);
return 0;
} Java
// Java implementation of the approach
import java.util.*;
class GFG
{
// Maximum possible valid number
static int MAX = 543210;
// To store all the required number
// from the range [1, MAX]
static Vector ans = new Vector();
// Function that returns true if x
// satisfies the given conditions
static boolean isValidNum(String x)
{
// To store the digits of x
HashMap mp = new HashMap();
for (int i = 0; i < x.length(); i++)
{
// If current digit appears more than once
if (mp.containsKey(x.charAt(i) - '0'))
{
return false;
}
// If current digit is greater than 5
else if (x.charAt(i) - '0' > 5)
{
return false;
}
// Put the digit in the map
else
{
mp.put(x.charAt(i) - '0', 1);
}
}
return true;
}
// Function to generate all the required
// numbers in the range [1, MAX]
static void generate()
{
// Insert first 5 valid numbers
Queue q = new LinkedList();
q.add("1");
q.add("2");
q.add("3");
q.add("4");
q.add("5");
boolean flag = true;
// Inserting 0 externally because 0 cannot
// be the leading digit in any number
ans.add("0");
while (!q.isEmpty())
{
String x = q.peek();
q.remove();
// If x satisfies the given conditions
if (isValidNum(x))
{
ans.add(x);
}
// Cannot append anymore digit as
// adding a digit will repeat one of
// the already present digits
if (x.length() == 6)
continue;
// Append all the valid digits one by
// one and push the new generated
// number to the queue
for (int i = 0; i <= 5; i++)
{
String z = String.valueOf(i);
// Append the digit
String temp = x + z;
// Push the newly generated
// number to the queue
q.add(temp);
}
}
}
// Function to copmpare two Strings
// which represent a numerical value
static boolean comp(String a, String b)
{
if (a.length()== b.length())
{
int i = a.compareTo(b);
return i < 0 ? true : false;
}
else
return a.length() < b.length();
}
// Function to return the count of
// valid numbers in the range [l, r]
static int findcount(String l, String r)
{
// Generate all the valid numbers
// in the range [1, MAX]
generate();
// To store the count of numbers
// in the range [l, r]
int count = 0;
// For every valid number in
// the range [1, MAX]
for (int i = 0; i < ans.size(); i++)
{
String a = ans.get(i);
// If current number is within
// the required range
if (comp(l, a) && comp(a, r))
{
count++;
}
// If number is equal to either l or r
else if (a == l || a == r)
{
count++;
}
}
return count;
}
// Driver code
public static void main (String[] args)
{
String l = "1", r = "1000";
System.out.println(findcount(l, r));
}
}
// This code is contributed by PrinciRaj1992 Python3
# Python3 implementation of the approach
from collections import deque
# Maximum possible valid number
MAX = 543210
# To store all the required number
# from the range [1, MAX]
ans = []
# Function that returns true if x
# satisfies the given conditions
def isValidNum(x):
# To store the digits of x
mp = dict()
for i in range(len(x)):
# If current digit appears more than once
if (ord(x[i]) - ord('0') in mp.keys()):
return False
# If current digit is greater than 5
elif (ord(x[i]) - ord('0') > 5):
return False
# Put the digit in the map
else:
mp[ord(x[i]) - ord('0')] = 1
return True
# Function to generate all the required
# numbers in the range [1, MAX]
def generate():
# Insert first 5 valid numbers
q = deque()
q.append("1")
q.append("2")
q.append("3")
q.append("4")
q.append("5")
flag = True
# Inserting 0 externally because 0 cannot
# be the leading digit in any number
ans.append("0")
while (len(q) > 0):
x = q.popleft()
# If x satisfies the given conditions
if (isValidNum(x)):
ans.append(x)
# Cannot append anymore digit as
# adding a digit will repeat one of
# the already present digits
if (len(x) == 6):
continue
# Append all the valid digits one by
# one and append the new generated
# number to the queue
for i in range(6):
z = str(i)
# Append the digit
temp = x + z
# Push the newly generated
# number to the queue
q.append(temp)
# Function to copmpare two strings
# which represent a numerical value
def comp(a, b):
if (len(a) == len(b)):
if a < b:
return True
else:
return len(a) < len(b)
# Function to return the count of
# valid numbers in the range [l, r]
def findcount(l, r):
# Generate all the valid numbers
# in the range [1, MAX]
generate()
# To store the count of numbers
# in the range [l, r]
count = 0
# For every valid number in
# the range [1, MAX]
for i in range(len(ans)):
a = ans[i]
# If current number is within
# the required range
if (comp(l, a) and comp(a, r)):
count += 1
# If number is equal to either l or r
elif (a == l or a == r):
count += 1
return count
# Driver code
l = "1"
r = "1000"
print(findcount(l, r))
# This code is contributed by Mohit KumarC#
// C# implementation of the approach
using System;
using System.Collections.Generic;
class GFG
{
// Maximum possible valid number
static int MAX = 543210;
// To store all the required number
// from the range [1, MAX]
static List ans = new List();
// Function that returns true if x
// satisfies the given conditions
static bool isValidNum(String x)
{
// To store the digits of x
Dictionary mp = new Dictionary();
for (int i = 0; i < x.Length; i++)
{
// If current digit appears more than once
if (mp.ContainsKey(x[i] - '0'))
{
return false;
}
// If current digit is greater than 5
else if (x[i] - '0' > 5)
{
return false;
}
// Put the digit in the map
else
{
mp.Add(x[i] - '0', 1);
}
}
return true;
}
// Function to generate all the required
// numbers in the range [1, MAX]
static void generate()
{
// Insert first 5 valid numbers
Queue q = new Queue();
q.Enqueue("1");
q.Enqueue("2");
q.Enqueue("3");
q.Enqueue("4");
q.Enqueue("5");
bool flag = true;
// Inserting 0 externally because 0 cannot
// be the leading digit in any number
ans.Add("0");
while (q.Count!=0)
{
String x = q.Peek();
q.Dequeue();
// If x satisfies the given conditions
if (isValidNum(x))
{
ans.Add(x);
}
// Cannot append anymore digit as
// adding a digit will repeat one of
// the already present digits
if (x.Length == 6)
continue;
// Append all the valid digits one by
// one and push the new generated
// number to the queue
for (int i = 0; i <= 5; i++)
{
String z = i.ToString();
// Append the digit
String temp = x + z;
// Push the newly generated
// number to the queue
q.Enqueue(temp);
}
}
}
// Function to copmpare two Strings
// which represent a numerical value
static bool comp(String a, String b)
{
if (a.Length == b.Length)
{
int i = a.CompareTo(b);
return i < 0 ? true : false;
}
else
return a.Length < b.Length;
}
// Function to return the count of
// valid numbers in the range [l, r]
static int findcount(String l, String r)
{
// Generate all the valid numbers
// in the range [1, MAX]
generate();
// To store the count of numbers
// in the range [l, r]
int count = 0;
// For every valid number in
// the range [1, MAX]
for (int i = 0; i < ans.Count; i++)
{
String a = ans[i];
// If current number is within
// the required range
if (comp(l, a) && comp(a, r))
{
count++;
}
// If number is equal to either l or r
else if (a == l || a == r)
{
count++;
}
}
return count;
}
// Driver code
public static void Main (String[] args)
{
String l = "1", r = "1000";
Console.WriteLine(findcount(l, r));
}
}
// This code is contributed by Princi Singh 输出：
130