【小米】二维定长滑动窗口

返回输入二维字符矩阵中班3*3子矩阵中含有xiaomi字符的个数，保证矩阵大小>=3;
输入：
4 4
xiaq
oime
xaic
cadf
输出
2

思路:

• 读入为char[][], 用nextline().toCharArray()给char[i]
• 按行向下, 按列向右, 先cmp匹配一个初始的3*3; 如00–2,2;
• row = 0, 往右, 限制为right
• row的限制,i+3<=n, 即边界判断;

代码块

import java.util.HashMap;
import java.util.LinkedList;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int m = sc.nextInt();
        sc.nextLine();
        char[][] chars = new char[4][4];
        for (int i = 0; i < n; i++) {
            chars[i] = sc.nextLine().toCharArray();
        }
        System.out.println(solution(chars));
    }


    //3*3的matrix,xiaomi
    private static int solution(char[][] strings) {

        HashMap<Character, Integer> need = new HashMap<>();
        HashMap<Character, Integer> window = new HashMap<>();
        String p = "xiaomi";
        for (char c : p.toCharArray()) {
            need.put(c, need.getOrDefault(c, 0) + 1);
        }

//        System.out.println(p);

        int left = 0, right = 0;//[)
        int valid = 0;

        int ans = 0;

        int k = 3;
        //00-33

        for (int i = 0; i+3 <= strings.length; i++) {
            window.clear();
            valid = cmp(i, strings, window, need, k);
            right = 3;left = 0;
            while (right<strings[0].length){
//                System.out.println("valid=" + valid);

                if (valid == need.size()) ans++;
                //判断是否满足 然后移动
                for (int j = i; j < i+3; j++) {
                    char c = strings[j][right];
                    if (need.containsKey(c)){
                        window.put(c,window.getOrDefault(c,0)+1);
                        if (window.get(c).equals(need.get(c))) valid++;
                    }

                    //移除
                    char d = strings[j][left];
                    if (need.containsKey(d)){
                        if (window.get(d).equals(need.get(d))) valid--;
                        window.put(d,window.get(d)-1);
                    }
                }
                right++;left++;
            }
        }


        return ans;
    }

    /**
     *
     * @param strings 原字符
     * @param window 窗口值
     * @param need 需要匹配
     * @param k 窗口长度
     */
    public static int cmp(int startX,char[][] strings,HashMap<Character,Integer> window,HashMap<Character,Integer> need,int k){
        //valid 满足字符数
        int valid = 0;
        for (int i = startX; i < startX+k; i++) {
            for (int j = 0; j < k; j++) {
                char c = strings[i][j];
                if (need.containsKey(c)){
                    window.put(c, window.getOrDefault(c, 0) + 1);
                    if (window.get(c).equals(need.get(c))) valid++;
                }
            }
        }
        return valid;
    }
    private static void func(LinkedList<Integer> ans) {
        System.out.println(ans);
    }


}
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