OJ-2:区间问题【九度1554】

package jobdu.wangdao;

import java.util.Scanner;

/**
 * 题目描述： 给定一个数组，判断数组内是否存在一个连续区间，使其和恰好等于给定整数k。
 * 
 */
public class Question1554 {

    private static void solve(int[] array, int k) {
        boolean find = false;
        for (int i = 0; i < array.length; i++) {
            if (!find) {
                int sum = 0;
                for (int j = i; j < array.length; j++) {
                    sum += array[j];
                    if (sum == k) {
                        find = true;
                        System.out.println((i + 1) + " " + (j + 1));
                        break;
                    }
                }
            }
        }
        if (!find)
            System.out.println("No");
    }

    public static void main(String[] args) {

        @SuppressWarnings("resource")
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            int n = scanner.nextInt();
            int[] array = new int[n];
            for (int i = 0; i < n; i++) {
                array[i] = scanner.nextInt();
            }
            int k = scanner.nextInt();
            solve(array, k);
        }
    }
}

package jobdu.wangdao;

import java.io.IOException;
import java.io.StreamTokenizer;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * 题目描述： 给定一个数组，判断数组内是否存在一个连续区间，使其和恰好等于给定整数k。
 * 
 */
public class Question1554 {

    /**
     * 暴力求和比较
     * 
     * @param array
     * @param k
     * @return
     */
    public static Section solve(int[] array, int k) {
        boolean find = false;
        for (int i = 0; i < array.length; i++) {
            if (!find) {
                int sum = 0;
                for (int j = i; j < array.length; j++) {
                    sum += array[j];
                    if (sum == k) {
                        find = true;
                        System.out.println((i + 1) + " " + (j + 1));
                        return new Section(i + 1, j + 1);
                    }
                }
            }
        }
        if (!find)
            System.out.println("No");
        return null;
    }

    public static Section solve2(int[] array, int k) {
        int[] sumList = new int[array.length];// 先计算出前0-i个数的和存入sumList
        Map<Integer, List<Integer>> map = new HashMap<Integer, List<Integer>>();
        // 记录前i个数的和和值相同的下标
        int sum = 0;
        for (int i = 0; i < array.length; i++) {
            sum = sum + array[i];
            sumList[i] = sum;
            if (map.containsKey(sum)) {// 将和的下标存入map
                List<Integer> indexList = map.get(sum);
                indexList.add(i);
            } else {
                List<Integer> indexList = new ArrayList<Integer>();
                indexList.add(i);
                map.put(sum, indexList);
            }
        }

        boolean find = false;
        List<Section> list = new ArrayList<Section>();
        for (int j = 0; j < sumList.length; j++) {
            int sumi = sumList[j];// 当前遍历的前j个数的和为sumi
            if (sumi == k) {// 如果前j个数的和就是k,那么直接为一组解
                Section node = new Section(1, (j + 1));
                list.add(node);// 加入解集合
                find = true;
                continue;
            }
            int temp = sumi + k;// 计算出对应的和已保证a[i]-a[j]=k
            if (map.containsKey(temp) && map.get(temp).size() > 0) {
                // 如果存在a[i]-a[j]=k，那么从第j+1个数到第i个数之和就为k,这里下标从0开始
                int start = j + 2;
                int end = -1;
                for (Integer integer : map.get(temp)) {// 从和相同的下标中选离j最近比i大的下标作为最后的解
                    if (integer >= j) {
                        end = integer + 1;
                        break;
                    }
                }
                if (end >= 0) {
                    list.add(new Section(start, end));
                    find = true;
                }
            }
        }

        if (!find)
            System.out.println("No");
        else {
            Collections.sort(list);// 对可能的解做一次排序，找到符合题意的解
            Section section = list.get(0);
            System.out.println(section.start + " " + section.end);
            return section;
        }
        return null;
    }

    /**
     * 确保List的排序
     * 
     */
    public static class Section implements Comparable<Section> {
        int start, end;

        public Section(int start, int end) {
            this.start = start;
            this.end = end;
        }

        @Override
        public int compareTo(Section o) {
            if (this.start == o.start)
                return this.end - o.end;
            return this.start - o.start;
        }

    }

    public static void main(String[] args) throws IOException {

        @SuppressWarnings("deprecation")
        StreamTokenizer st = new StreamTokenizer(System.in);
        while (st.nextToken() != StreamTokenizer.TT_EOF) {
            int n = (int) st.nval;
            int[] array = new int[n];
            for (int i = 0; i < n; i++) {
                st.nextToken();
                array[i] = (int) st.nval;
            }
            st.nextToken();
            int k = (int) st.nval;
            solve2(array, k);
        }
    }
}