codewars练习（javascript）-2021/3/10

codewars-js练习

2021/3/10

github 地址

my github地址，上面有做的习题记录，不断更新…

【1】<6kyu>【Multiplication table】

Your task, is to create NxN multiplication table, of size provided in parameter.

example：

1 2 3
2 4 6
3 6 9
for given example, the return value should be: [[1,2,3],[2,4,6],[3,6,9]]

solution

<script type="text/javascript">
    multiplicationTable = function(size) {
        // console.log(size)s
        var temp = [];
        for(var i=1 ;i<=size;i++){
            for(var j=1;j<=size;j++){
                temp.push(i*j);
            }
        }
        var result = [];
        for(var z=0;z<temp.length;z+=size){
            result.push(temp.slice(z,z+size));
        }
        return result
    }
        
    // 验证
    console.log(multiplicationTable(3));//[[1,2,3], [2,4,6], [3,6,9]]
</script>

<script type="text/javascript">
    multiplicationTable = function(size) {
        // console.log(size)
        var result = [];
        for(var i=0 ;i<size;i++){
            result[i] = [];
            for(var j=0;j<size;j++){
                result[i][j]= (i+1)*(j+1);
            }
        }
        return result
    }
        
    // 验证
    console.log(multiplicationTable(3));//[[1,2,3], [2,4,6], [3,6,9]]
</script>

【2】<5kyu>【Make an increasing sequence】

Give you an integer array arr. Your task is remove the least number of elements, so that the array into an increasing sequence. The result is the increasing sequence.

给你一个整数数组arr。您的任务是删除最少数量的元素，使数组成为一个递增的序列。结果是递增序列

所有元素都是正整数;如果存在多个解决方案，则返回第一个(从左到右，通过索引比较，选择最小的);如果arr已经是递增序列，则返回本身;如果arr是递减序列，则返回一个只包含第一个元素的数组。

example：

arr = [1,100,2,3,100,4,5] 
should return: [1,2,3,4,5]
(remove elements: 100,100)

solution

<script type="text/javascript">
    function increasingSequence(arr){
        var max=0, p=0, S=arr.length;
        var cnt=arr.map(_=>1), jump=arr.map(_=>-1);
  
        // 倒序进行比较
        for(var i=S-2;i>=0;i--){
            var v=arr[i], c=cnt[i];
            for(var j=i+1;c-1+j<S;j++) 
                if(v<arr[j] && c<=cnt[j]){
                    cnt[i]=c=cnt[j]+1; jump[i]=j;
                }
            if(max<=c){ max=c; p=i; }
        }
        var out=[];
        while(p!=-1){
            out.push(arr[p]);
            p=jump[p];
        }
        return out;
    }
        
    // 验证
    // console.log(increasingSequence([1, 1, 1, 2]));// [1, 2]
    console.log(increasingSequence([186,186,150,200,160,130,197,220]));// [150,160,197,220]
    // console.log(increasingSequence([1,2,3,4,5]));// [1,2,3,4,5]
    // console.log(increasingSequence([5,4,3,2,1]));//[5]
</script>

【1】<7kyu>【Largest 5 digit number in a series】

example：

283910 --> 1234567890 //0

solution

<script type="text/javascript">
    function solution(digits){
        let answer = 0;
  
        for (let i=0; i<digits.length; i++){
            let number = digits.substr(i, 5);  //each loop iteration pulls the next 5 digits into a substring
            if(Number(number) > answer){       //convert to number and compare against answer
                answer = Number(number);
            }
        }
        return answer;
        }
        
    // 验证
    console.log(solution(283910))//0
</script>