聪聪工作室---Codingbat练习---Map-2 总结

import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

public class word0 {

    public static void main(String[] args) {

        String[] strings = { "addd", "bddd", "b", "a", "a", "b", "b", "a", "a", "c", "c", "b", "b", "a", "a", "b", "b",
                "a", "a", "c", "c" };

        // System.out.println(word0(strings));

        //

        // System.out.println(wordMultiple(strings));

        // System.out.println(wordLen(strings));
        // System.out.println(firstChar(strings));
        // allSwap(strings);
        // System.out.println(Arrays.toString(strings));

        // System.out.println(pairs(strings));

        // System.out.println(wordAppend(strings));
        System.out.println(Arrays.toString(firstSwap(strings)));

    }

    public static Map<String, Integer> word0(String[] strings) {
        HashMap<String, Integer> map = new HashMap<String, Integer>();
        for (String s : strings) {
            map.put(s, 0);
        }

        return map;

    }

word0.png

    public static Map<String, Integer> wordCount(String[] strings) {
        HashMap<String, Integer> map = new HashMap<String, Integer>();

        for (String s : strings) { // s是指strings数组中的数；
            System.out.println(map.get(s)); // map.get() 自动统计在map数组中元素出现的次数，从0开始

            if (map.get(s) != null) {
                map.put(s, map.get(s) + 1);// 从0开始，所以要加1，s对应的关联值加1 变成2 ，因为null+1
                                            // 不知道运算方法

            } else {
                map.put(s, 1);// 如果是等于null 的，出现1次后，自动赋值为1
            }

        }
        System.out.println("统计输出： ");

        for (String s : map.keySet()) { // 把数组中的元素罗列出来，不允许重复
            System.out.println("  " + s + " : " + map.get(s));// s是罗列出的元素
                                                                // ，map.get(s)
                                                                // 在上一步循环中已经进行+1处理，直接映射数组元素的关联值，也就是这个数组中所存在的相同元素的个数
        }
        return map;

    }

wordCount.png

    public static Map<String, Boolean> wordMultiple(String[] strings) {
        HashMap<String, Integer> map1 = new HashMap<String, Integer>();

        for (String s : strings) {
            if (map1.get(s) == null) {
                map1.put(s, 1);
            } else if (map1.get(s) != null) {
                map1.put(s, map1.get(s) + 1);
            }

        }

        Map<String, Boolean> map2 = new HashMap<String, Boolean>();
        for (String s1 : map1.keySet()) {

            if (map1.get(s1) % 2 >= 0) {
                map2.put(s1, true);
            } else {
                map2.put(s1, false);
            }
        }

        return map2;

    }

wordMultiple.png

    public static Map<String, Integer> wordLen(String[] strings) {

        HashMap<String, Integer> map3 = new HashMap<String, Integer>();

        for (String s : strings) {

            map3.put(s, 0);
        }

        for (String s1 : map3.keySet()) {
            System.out.println(s1);

            int size = s1.length();

            map3.put(s1, size);

        }
        return map3;

    }

wordLen.png

    public static Map<String, String> firstChar(String[] strings) {

        HashMap<String, String> map = new HashMap<String, String>();
        for (String s : strings) {
            String f = s.charAt(0) + "";
            if (!map.containsKey(f)) {
                map.put(f, s);
            } else {
                map.put(f, map.get(f) + s);
            }
        }
        return map;

    }

firstChar.png

    public static String[] allSwap(String[] strings) {

        HashMap<String, Integer> map = new HashMap<String, Integer>();
        for (int i = 0; i < strings.length; i++) {
            String f = strings[i].charAt(0) + "";
            if (!map.containsKey(f)) {
                map.put(f, i);
            } else {
                String temp = strings[i];
                strings[i] = strings[map.get(f)];
                strings[map.get(f)] = temp;
                map.remove(f);
            }

        }

        return strings;
    }

allSwap.png

    public static Map<String, String> pairs(String[] strings) {
        HashMap<String, String> map = new HashMap<String, String>();
        for (int i = 0; i < strings.length; i++) {
            String index = strings[i].charAt(0) + "";
            String end = strings[i].charAt(strings[i].length() - 1) + "";
            map.put(index, end);
        }
        return map;

    }

pairs.png

    public static String wordAppend(String[] strings) {
        HashMap<String, Integer> map = new HashMap<String, Integer>();
        String result = "";
        for (String s : strings) {

            if (!map.containsKey(s)) {
                map.put(s, 1);
            } else {
                map.put(s, map.get(s) + 1);

            }
            System.out.println(s + ":" + map.get(s));
            if (map.get(s) == 2) {
                result = result + s;
                map.remove(s);
            }
        }

        return result;

    }

wordAppend.png

    public static String[] firstSwap(String[] strings) {


        HashMap<String,Integer> map=new HashMap<String,Integer>();
        for (int i = 0; i < strings.length; i++) {
            String f=strings[i].charAt(0)+"";
            if(!map.containsKey(f)){
                map.put(f, i);
            }else if(map.get(f)==-1){
                String temp=strings[i];
                strings[i]=strings[map.get(f)];
                strings[map.get(f)]=temp;
                map.put(f, -1);
            }
        }
        return strings;
        
    }
}

firstSwap.png

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