题解 | 【模板】双指针

import java.util.*;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        int arrayLength = in.nextInt();
        int[] array = new int[arrayLength];
        for(int i = 0; i < arrayLength; i++) {
            array[i] = in.nextInt();
        }
        int currentMaxLength = 1;
        int currentStartIndex = 0;
        Set<Integer> valueSet =new HashSet<>();
        List<Integer> startIndexList = new ArrayList<>();
        startIndexList.add(0);
        valueSet.add(array[0]);
        int i = 1; 
        while (true) {
            if (i == array.length) {
                break;
            }
            if (valueSet.contains(array[i])) {
                int preValue = array[currentStartIndex];
                valueSet.remove(preValue);
                currentStartIndex++;
       
            } else {
                valueSet.add(array[i]);
                int curentLength  = i - currentStartIndex + 1;
                if (curentLength > currentMaxLength) {
                    currentMaxLength = curentLength;
                    startIndexList.clear();
                    startIndexList.add(currentStartIndex);
                } else if (curentLength == currentMaxLength){
                    startIndexList.add(currentStartIndex);
                }
                i++;
            }
        }

        System.out.println(startIndexList.size());
        for(int startIndex : startIndexList) {
             int printStartIndex = startIndex + 1;
             int printEndIndex = startIndex + currentMaxLength;
             System.out.println(printStartIndex + " " + printEndIndex);
        }
    }
}