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计算机视觉面试题-01

陈情雅雅 2023-11-27 阅读 49

写在开头

本文参考原文

BitMap

Redis中的BitMap同我们所使用的算法当中的bitmap是相同的道理。简单来说就是使用二进制位,每一位的0/1状态表示信息。
二进制表示的优势:
大大节省空间。如两位二进制位00、01、10、11可以表示四种状态

Redis当中提供了bitmap的数据结构,并有相关的操作命令。通过这命令的搭配,可以实现不同的逻辑应用。

Redis中BitMap命令

Redis提供了SETBIT、GETBIT、BITCOUNT、BITOP四个常用命令用于处理二进制位数组。

具体例子如下:


127.0.0.1:6379> SETBIT first 0 1    # 0000 0001
(integer) 0
127.0.0.1:6379> SETBIT first 3 1    # 0000 1001
(integer) 0
127.0.0.1:6379> SETBIT first 0 0    # 0000 1000
(integer) 1
 
127.0.0.1:6379> GETBIT first 0
(integer) 0
127.0.0.1:6379> GETBIT first 3
(integer) 1
 
127.0.0.1:6379> BITCOUNT first      # 0000 1000
(integer) 1
127.0.0.1:6379> SETBIT first 0 1    # 0000 1001
(integer) 0
127.0.0.1:6379> BITCOUNT first      # 0000 1001
(integer) 2
127.0.0.1:6379> SETBIT first 1 1    # 0000 1011
(integer) 0
127.0.0.1:6379> BITCOUNT first      # 0000 1011
(integer) 3
 
127.0.0.1:6379> SETBIT x 3 1        
(integer) 0
127.0.0.1:6379> SETBIT x 1 1        
(integer) 0
127.0.0.1:6379> SETBIT x 0 1        # 0000 1011
(integer) 0
127.0.0.1:6379> SETBIT y 2 1        
(integer) 0
127.0.0.1:6379> SETBIT y 1 1        # 0000 0110
(integer) 0
127.0.0.1:6379> SETBIT z 2 1        
(integer) 0
127.0.0.1:6379> SETBIT z 0 1        # 0000 0101
(integer) 0
 
127.0.0.1:6379> BITOP AND andRes x y z    #0000 0000
(integer) 1
127.0.0.1:6379> BITOP OR orRes x y z      #0000 1111
(integer) 1
127.0.0.1:6379> BITOP XOR x y z           #0000 1000
(integer) 1
 
# 对给定的位数组进行按位取反
127.0.0.1:6379> SETBIT value 0 1
(integer) 0
127.0.0.1:6379> SETBIT value 3 1            #0000 1001
(integer) 0
127.0.0.1:6379> BITOP NOT notValue value    #1111 0110
(integer) 1

具体每种命令的详解可见参考原文。

实现github打卡功能

功能分析:

代码实现:

生成模拟数据

public void genTestData() {
    if(redisUtils.isExist(CommonConstant.KEY)){
        return;
    }
    // 获取当前年的总天数
    int days = getDays();
    for (int i = 0; i < days; i++) {
        int random = ThreadLocalRandom.current().nextInt(64);
        // 生成随机数表示每天的PR次数
        String binaryString = Integer.toBinaryString(random);
        if (binaryString.length() < 8) {
            // 填充0
            if(binaryString.length() == 0){binaryString = "00000000";}
            else if(binaryString.length() == 1){binaryString = "0000000"+binaryString;}
            else if(binaryString.length() == 2){binaryString = "000000"+binaryString;}
            else if(binaryString.length() == 3){binaryString = "00000"+binaryString;}
            else if(binaryString.length() == 4){binaryString = "0000"+binaryString;}
            else if(binaryString.length() == 5){binaryString = "000"+binaryString;}
            else if(binaryString.length() == 6){binaryString = "00"+binaryString;}
            else if(binaryString.length() == 7){binaryString = "0"+binaryString;}
        }
        char[] chars = binaryString.toCharArray();
        for (int j = 0; j < chars.length; j++) {
            // 设置BitMap
            redisUtils.setBit(CommonConstant.KEY,i*8+j,chars[j]);
        }
    }
}
 
/**
 * 获取当前年的总天数
 * @return days 总天数
 */
private int getDays(){
    Calendar calOne = Calendar.getInstance();
    int year = calOne.get(Calendar.YEAR);
    System.out.println(year);
    Calendar calTwo = new GregorianCalendar(year, 11, 31);
    return calTwo.get(Calendar.DAY_OF_YEAR);
}

获取Redis bitmap中的数据

public List<String> getPushData() {
    List<String> res = new ArrayList<>(366);
    // 没有数据就先造数据
    genTestData();
    int days = getDays();
    for(long i=0;i<days;i++){
        StringBuilder sb = new StringBuilder();
        for (int j = 0; j < 8; j++) {
            String bit = redisUtils.getBit(CommonConstant.KEY, i * 8 + j);
            sb.append(bit);
        }
        // 直接返回二进制串,前端转换为十进制
        res.add(sb.toString());
    }
    return res;
}

前端展示

<script type="text/javascript">
    var chartDom = document.getElementById('main');
    var myChart = echarts.init(chartDom);
    var option;
 
    function getVirtulData(year) {
        var date = +echarts.number.parseDate(year + '-01-01');
        var end = +echarts.number.parseDate(+year + 1 + '-01-01');
        var dayTime = 3600 * 24 * 1000;
        var data = [];
        $.ajax({
            "url":'http://localhost:8080/test/getPushData',
            "async":false, // ajax同步获取
            success:function (res){
                for (let time = date,k=0; time < end && k < res.data.length; time += dayTime,k++) {
                    data.push([
                        echarts.format.formatTime('yyyy-MM-dd', time),
                        parseInt(res.data[k],2)//客户端完成进制转换,不放在服务端完成
                    ]);
                }
            }
        })
 
        return data;
    }
    option = {
        title: {
            top: 30,
            left: 'left',
            text: 'BitMap Demo'
        },
        tooltip: {},
        visualMap: {
            min: 0,
            max: 32,
            type: 'piecewise',
            orient: 'horizontal',
            left: 'right',
            top: 220,
            pieces: [
                {min: 0, max: 0,label:"less"},
                {min: 1, max: 10,label:" "},
                {min: 1, max: 20,label:" "},
                {min: 21, max: 40,label:" "},
                {min: 41, max: 64,label:"more"},
            ],
            inRange: {
                color: [ '#EAEDF0', '#9AE9A8', '#41C363', '#31A14E', '#206D38' ],//颜色设置 
                colorAlpha: 0.9,//透明度
            }
        },
        calendar: {
            top: 120,
            left: 30,
            right: 30,
            cellSize: 13,
            range: '2022',
            splitLine: { show: false },//不展示边线
            itemStyle: {
                borderWidth: 0.5
            },
            yearLabel: { show: false }
        },
        series: {
            type: 'heatmap',
            coordinateSystem: 'calendar',
            data: getVirtulData('2022')
        }
    };
 
    option && myChart.setOption(option);
</script>

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