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  1. Prepare
  2. Data Structures
  3. Queues
  4. Down to Zero II
  5. Discussions

Down to Zero II

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231 Discussions

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  • ambuj_yadav_che1
     + 0 comments

    how is editorial code working q =10^5 n =10^6

    for each query we are doing memset so q*n then how is it working or is there anything that i am missing here

  • axmadjonovulugb1
     + 2 comments

    TESTCASES ARE WRONG. DONT BE SURPRISED. e.g: for 86 expected output is 7. but my output was 8: 86->43->42->7->6->3->2->1->0.!

  • vishnubabu94in
     + 0 comments

    js

    const map = { 0: 0, 1: 1 };
function downToZero(n) {
    for (let i = 2; i <= n; i++) {
        if (map[i]) continue;

        let a = 2;
        let min = map[i - 1];
        let b;
        while (a <= (b = i / a)) {
            if (Math.floor(b) === b) {
                min = Math.min(min, map[b]);
            }
            a++;
        }
        map[i] = min + 1;
    }
    return map[n];
}

  • Dmitry_Strakhov
     + 1 comment

    Here is my DP solution (C# code). Take a look:

    public static int DownToZero(int n) {
    return new DownToZeroSolution().Solve(n);
}
    
class DownToZeroSolution {
    static int calculated_N;
    static readonly int[] solutions;

    static DownToZeroSolution() {
        calculated_N = 1;
        solutions = new int[1_000_001];
        solutions[1] = 1;
    }
    public int Solve(int n) {
        if(n <= calculated_N) return solutions[n];

        for(int i = calculated_N + 1; i <= n; i++) {
            solutions[i] = CalculateItem(i);
        }
        calculated_N = n;
        return solutions[n];
    }
    static int CalculateItem(int n) {
        int min = solutions[n - 1];
        int d_start;
        int d_step;

        if((n & 1) == 1) {
            d_start = 3;
            d_step = 2;
        }
        else {
            d_start = 2;
            d_step = 1;
        }
        
        int topN = (int)(Math.Sqrt(n) + 0.1);

        // n = d1*d2
        for(int d1 = d_start; d1 <= topN; d1 += d_step) {
            if(n % d1 == 0)
                min = Math.Min(min, solutions[Math.Max(d1, n / d1)]);
        }
        return 1 + min;
    }
}

  • shridhar_thorat1
     + 1 comment

    I can't figure out how to fix this code. It only works for 2 tests. For the ones it fails it's usually just one more move than expected

    def downToZero(n):
    moves = 0
    while n != 0:
        a = 1
        b = 1
        if n == 1:
            n -= 1
            moves += 1
            break
        # calculate factors until a < b
        for num in range(n-1, 1, -1):
            if n % num == 0:
                a = num
                b = n // num
                if a < b:
                    break

        if (a == 1) or (a == n):
            n -= 1
        else:
            n = max(a, b)
        moves += 1

    return moves