从字符串中查找不同年份的总数

给定一个包含单词和日期的字符串，任务是找到该字符串中提到的不同年份的总数。
注意：假设日期为“DD-MM-YYYY”格式。

例子：

Input:  str = "UN was established on 24-10-1945.
                India got freedom on 15-08-1947."
Output: 2
2 distinct years i.e. 1945 and 1947 have been referenced.

Input: str = "Soon after the world war 2 ended on 02-09-1945.
        The UN was established on 24-10-1945."
Output: 1
Only 1 Year, i.e 1945 has been referenced .

方法：

1. 开始遍历字符串。
2. 检查当前字符是否为数字。将其存储在另一个字符串中，即 dateString。
3. 检查当前字符是否为'-'，然后删除dateString中存储的字符。
4. 检查dateString的长度是否等于4，则表示是一年。
5. 将那一年存储在 unordered_set 中。
6. 返回 unordered_set 的大小，因为它只包含唯一值。

下面是上述方法的实现：

C++

// C++ Program to find the total
// number of distinct years
#include 
using namespace std;
 
// function to find the total
// number of distinct years
int distinct_year(string str)
{
    string str2 = "";
 
    unordered_set uniqueDates;
 
    for (int i = 0; i < str.length(); i++) {
 
        if (isdigit(str[i])) {
            str2.push_back(str[i]);
        }
 
        // if we found - then clear the str2
        else if (str[i] == '-') {
            str2.clear();
        }
 
        // if length of str2 becomes 4
        // then store it in a set
        else if (str2.length() == 4) {
            uniqueDates.insert(str2);
            str2.clear();
        }
         
        // else clear the string.
        else{
           str2.clear();
        }
    }
 
    // return the size of set
    return uniqueDates.size();
}
 
// Driver code
int main()
{
    string str = "UN was established on 24-10-1945."
                 "India got freedom on 15-08-1947.";
 
    cout << distinct_year(str);
 
    return 0;
}

Java

import java.util.HashSet;
import java.util.Set;
 
// Java Program to find the total
// number of distinct years
public class GFG {
 
// function to find the total
// number of distinct years
    static int distinct_year(String str) {
        String str2 = "";
 
        Set uniqueDates = new HashSet<>();
 
        for (int i = 0; i < str.length(); i++) {
 
            if (Character.isDigit(str.charAt(i))) {
                str2 += (str.charAt(i));
            }
 
            // if we found - then clear the str2
            if (str.charAt(i) == '-') {
                str2 = "";
            }
 
            // if length of str2 becomes 4
            // then store it in a set
            if (str2.length() == 4) {
                uniqueDates.add(str2);
                str2 = "";
            }
        }
 
        // return the size of set
        return uniqueDates.size();
    }
 
// Driver code
    static public void main(String[] args) {
        String str = "UN was established on 24-10-1945."
                + "India got freedom on 15-08-1947.";
 
        System.out.println(distinct_year(str));
    }
}

Python3

# Python3 Program to find the total
# number of distinct years
 
# function to find the total
# number of distinct years
import re
def distinct_years(str):
    str2 = ""
 
    uniqueDates = set()
    pattern="[0-9][0-9]-[0-9][0-9]-[0-9][0-9][0-9][0-9]"
    dates = re.findall(pattern,str)
    for item in dates:
        uniqueDates.add(item.split('-')[-1])
    # return the size of se
    return len(uniqueDates)
 
# Driver code
if __name__ == "__main__":
    str = "UN was established on 24-10-1945.\
           India got freedom on 15-08-1947."
 
    print(distinct_years(str))
 
# This code is contributed by
# sanjeev2552

C#

// C# Program to find the total
// number of distinct years
using System;
using System.Collections.Generic;
 
class GFG
{
 
    // function to find the total
    // number of distinct years
    static int distinct_year(String str)
    {
        String str2 = "";
 
        HashSet uniqueDates = new HashSet();
 
        for (int i = 0; i < str.Length; i++)
        {
            if (char.IsDigit(str[i]))
            {
                str2 += (str[i]);
            }
 
            // if we found - then clear the str2
            if (str[i] == '-')
            {
                str2 = "";
            }
 
            // if length of str2 becomes 4
            // then store it in a set
            if (str2.Length == 4)
            {
                uniqueDates.Add(str2);
                str2 = "";
            }
        }
 
        // return the size of set
        return uniqueDates.Count;
    }
 
    // Driver code
    static public void Main(String[] args)
    {
        String str = "UN was established on 24-10-1945." +
                     "India got freedom on 15-08-1947.";
 
        Console.WriteLine(distinct_year(str));
    }
}
 
// This code is contributed by Princi Singh

Javascript

 
// Javascript Program to find the total
// number of distinct years
 
// function to find the total
// number of distinct years
function distinct_year(str)
{
    var str2 = "";
 
    var uniqueDates = new Set();
 
    for (var i = 0; i < str.length; i++) {
 
        if (parseInt(str[i])) {
            str2+=(str[i]);
        }
 
        // if we found - then clear the str2
        if (str[i] == '-') {
            str2 = "";
        }
 
        // if length of str2 becomes 4
        // then store it in a set
        if (str2.length == 4) {
            uniqueDates.add(str2);
            str2 = "";
        }
    }
 
    // return the size of set
    return uniqueDates.size;
}
 
// Driver code
var str = "UN was established on 24-10-1945." +
             "India got freedom on 15-08-1947.";
document.write( distinct_year(str));
 

输出

2

时间复杂度： O(n)