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  1. Practice
  2. Algorithms
  3. Implementation
  4. Circular Array Rotation
  5. Discussions

Circular Array Rotation

  • polmki99 + 7 comments

    What's the space and time efficiency for this code?

    n, k, m = map(int, input().strip().split())
arr = list(map(int, input().strip().split()))
k %= n
arr = arr[-k:] + arr[:-k]
for i in range(m):
    print(arr[int(input().strip())])
    • hgnisrednivrug + 0 comments

      wow!!! fast and easy way to done the problem..

    • Pr0gr3550 + 0 comments
      [deleted]
    • franchb1 + 0 comments

      Thank you!

      Now I know %=

    • amcavinue + 0 comments

      Really great solution!

    • nstoddar + 1 comment

      Thanks polmki99! Very clever implementation.

      Here it is in Javascript for those interested.

      function processData(input) {
    //Enter your code here
    var inputList = input.split('\n');
    var details = inputList[0].split(" ");
    var arrayIdx = inputList.slice(2);
    var targetArray = inputList[1].split(" ");
    
    var k = details[1]%details[0];
    
    targetArray = [].concat(targetArray.slice(-k),targetArray.slice(0,-k));
    
    arrayIdx.map(function(elem){return console.log(targetArray[elem]);});
}
      • murnun + 1 comment

        Nice one liner using the built in functions! Unfortunately, this still fails when k is higher than n (test case #4). You seem to be getting around it by overwriting k with: 

        var k = details[1]%details[0];

        I'm curious to see if there are other, more algorithmic solutions to this in Javascript.

        • matt_heisig + 1 comment

          This works in Javascript for all test cases:

          function main() {
    var n_temp = readLine().split(' ');
    var n = parseInt(n_temp[0]);
    var k = parseInt(n_temp[1]);
    var q = parseInt(n_temp[2]);
  
    a = readLine().split(' ');
    a = a.map(Number);
  
    for (var i=0; i<q; i++) {
      var m = readLine();
      console.log(a.slice(m-k%n)[0]);
    }
}
          • mehul_sachdeva7 + 1 comment

            when i ran my code only sample test cleared and rest failed

            function circularArrayRotation(a, k, queries) { 

    var res = [];
    var resind = 0;

    while (k > 0) {
        rotateArr();
        k--;
    }

    function rotateArr() {
        var i = 0;
        var lastel = a[a.length - 1];
        var temp1 = a[0];
        var temp2;

        while (i < a.length-1) {
            temp2 = a[i + 1];
            a[i + 1] = temp1;
            temp1 = temp2;
            i++;
        }

        a[0] = lastel;
    }

    for(var j in queries) {
        res[resind] = a[j];
        resind++;
    }

    return res;
		}

                I think some issue is in how i am returning the values, please help identify the error
            • mehul_sachdeva7 + 1 comment

              found out what the problem was, new JS code:

              function circularArrayRotation(a, k, queries) {

    var rarr = [];
    var aind = [];
    var res = [];

    for (var i = 0; i < a.length; i++){
        if ((i + k) < a.length) {
            aind[i] = i + k;
        } else {
            aind[i] = (i + k) % a.length;
        }
    }

    for (var j = 0; j < a.length; j++) {
        rarr[aind[j]] = a[j];
    }


    for (var k = 0; k < queries.length; k++){
        res[k] = rarr[queries[k]];
    }

    return (res);
}
              • tashk85 + 0 comments

                Hi, could you please explain what is happening here? Thanks

    • ryanlough + 0 comments
      [deleted]
    • mail2karthk07 + 0 comments

      how about my solution is it good..

      n,k,q = list(map(int, input().strip().split()))
a = list(map(int, input().strip().split()))
a = a[n-(k%n):]+a[0:n-(k%n)]
[print(a[int(input())]) for _ in range(q)]