C++程序查找不超过T的最长可能时间以解决所有问题
假设我们有一个包含N个元素的数组A。还有另一个数字T。假设Amal正在尝试参加一个编程比赛。它持续T分钟,并有N个问题。他需要A[i]时间来解决第i个问题。他将从N个问题中选择零个或多个问题来解决,以便总共花费不超过T分钟。我们必须找到解决他所选问题的最长时间。
因此,如果输入类似于T = 17;A = [2, 3, 5, 7, 11],则输出将为17,因为如果他选择前四个问题,则总共需要2 + 3 + 5 + 7 = 17分钟来解决它们,这是不超过T分钟的最长可能时间。
步骤
为了解决这个问题,我们将遵循以下步骤:
n := size of A Define an array b of size (n / 2) and c of size (n - n/2) for initialize i := 0, when i < n / 2, update (increase i by 1), do: b[i] := A[i] for initialize i := n / 2, when i < n, update (increase i by 1), do: c[i - n / 2] = A[i] Define an array B, C for bit in range 0 to 2^(n/2), increase bit after each iteration, do p := 0 for initialize i := 0, when i < n / 2, update (increase i by 1), do: if bit AND 2^i is non zero, then p := p + b[i] insert p at the end of B for bit in range 0 to 2^(n - n/2), increase bit after each iteration p := 0 for initialize i := 0, when i < n - n / 2, update (increase i by 1), do: if bit AND 2^i is non-zero, then p := p + c[i] insert p at the end of C mx := 0 sort the array C for initialize i := 0, when i < size of B, update (increase i by 1), do: if t - B[i] < 0, then: Ignore following part, skip to the next iteration itr = next larger element of (t - B[i]) in C (decrease itr by 1) mx := maximum of mx and (itr + B[i]) return mx
示例
让我们看看以下实现以获得更好的理解:
#include <bits/stdc++.h>
using namespace std;
int solve(int t, vector<int> A){
int n = A.size();
vector<int> b(n / 2), c(n - n / 2);
for (int i = 0; i < n / 2; i++)
b[i] = A[i];
for (int i = n / 2; i < n; i++)
c[i - n / 2] = A[i];
vector<int> B, C;
for (int bit = 0; bit < (1 << (n / 2)); bit++){
int p = 0;
for (int i = 0; i < n / 2; i++){
if (bit & (1 << i))
p += b[i];
}
B.push_back(p);
}
for (int bit = 0; bit < (1 << (n - n / 2)); bit++){
int p = 0;
for (int i = 0; i < n - n / 2; i++){
if (bit & (1 << i))
p += c[i];
}
C.push_back(p);
}
int mx = 0;
sort(C.begin(), C.end());
for (int i = 0; i < B.size(); i++){
if (t - B[i] < 0)
continue;
auto itr = upper_bound(C.begin(), C.end(), t - B[i]);
itr--;
mx = max(mx, *itr + B[i]);
}
return mx;
}
int main(){
int T = 17;
vector<int> A = { 2, 3, 5, 7, 11 };
cout << solve(T, A) << endl;
}输入
17, { 2, 3, 5, 7, 11 }输出
17
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