Make Target List with Increment and Double Operations - Amazon Top Interview Questions

Problem Statement :

You are given a list of non-negative integers target. Consider a list A of the same length as target containing all zeros initially. In one operation, you can increment one number in A, or double every number in A. Return the minimum number of operations required to turn A into target.


0 ≤ n ≤ 100,000 where n is the length of target

Example 1


target = [3, 2, 2]




First, we start with A = [0, 0, 0]

We increment A[0] and get [1, 0, 0]
We increment A[1] and get [1, 1, 0]
We increment A[2] and get [1, 1, 1]
We double every element and get [2, 2, 2]
We increment A[0] and get [3, 2, 2]

Example 2


target = [0, 0, 0, 0, 0]




A is already equal to target.

Solution :


                        Solution in C++ :

int solve(vector<int>& target) {
    map<int, int> c;
    for (int x : target) ++c[x];
    int ret = 0, b = 0;
    for (const auto& p : c) {
        int x = p.first, y = 0;
        while (x) {
            if (x % 2)
                ret += p.second, --x;
                x /= 2, ++y;
        b = max(b, y);
    return ret + b;

                        Solution in Python : 
class Solution:
    def solve(self, target):
        max_len, cnt_ones = 0, 0
        for n in target:
            bits = bin(n)
            max_len = max(max_len, len(bits) - 3)
            cnt_ones += bits.count("1")
        return max_len + cnt_ones

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