Task description
You are given integers K, M and a non-empty zero-indexed array A consisting of N integers. Every element of the array is not greater than M.
You should divide this array into K blocks of consecutive elements. The size of the block is any integer between 0 and N. Every element of the array should belong to some block.
The sum of the block from X to Y equals A[X] + A[X + 1] + ... + A[Y]. The sum of empty block equals 0.
The large sum is the maximal sum of any block.
For example, you are given integers K = 3, M = 5 and array A such that:
A[0] = 2
A[1] = 1
A[2] = 5
A[3] = 1
A[4] = 2
A[5] = 2
A[6] = 2
The array can be divided, for example, into the following blocks:
[2, 1, 5, 1, 2, 2, 2], [], [] with a large sum of 15;
[2], [1, 5, 1, 2], [2, 2] with a large sum of 9;
[2, 1, 5], [], [1, 2, 2, 2] with a large sum of 8;
[2, 1], [5, 1], [2, 2, 2] with a large sum of 6.
The goal is to minimize the large sum. In the above example, 6 is the minimal large sum.
Write a function:
function solution(K, M, A);
that, given integers K, M and a non-empty zero-indexed array A consisting of N integers, returns the minimal large sum.
For example, given K = 3, M = 5 and array A such that:
A[0] = 2
A[1] = 1
A[2] = 5
A[3] = 1
A[4] = 2
A[5] = 2
A[6] = 2
the function should return 6, as explained above.
Assume that:
- N and K are integers within the range [1..100,000];
- M is an integer within the range [0..10,000];
- each element of array A is an integer within the range [0..M].
Complexity:
- expected worst-case time complexity is O(N*log(N+M));
- expected worst-case space complexity is O(1), beyond input storage (not counting the storage required for input arguments).
Elements of input arrays can be modified.
function solution(K, M, A) {
var begin = A.reduce((a, v) => (a + v), 0)
begin = parseInt((begin+K-1)/K, 10);
var maxA = Math.max(A);
if (maxA > begin) begin = maxA;
var end = begin + M + 1;
var res = 0;
while(begin <= end) {
var mid = (begin + end) / 2;
var sum = 0;
var block = 1;
for (var ind in A) {
var a = A[ind];
sum += a;
if (sum > mid) {
++block;
if (block > K) break;
sum = a;
}
}
if (block > K) {
begin = mid + 1;
} else {
res = mid;
end = mid - 1;
}
}
return res;
}