用 C++ 使矩阵的所有元素相等所需的最小操作
问题陈述
给定一个整数 K 和一个 M x N 的矩阵,任务是找出使矩阵所有元素相等所需的最小操作数。在单次操作中,K 可以被添加到或从矩阵的任何元素中减去。
示例
If input matrix is: { {2, 4}, {20, 40} } and K = 2 then total 27 operations required as follows; Matrix[0][0] = 2 + (K * 9) = 20 = 9 operations Matrix[0][1] = 4 + (k * 8) = 20 = 8 operations Matrix[1][0] = 20 + (k * 10) = 40 = 10 operations
算法
1. Since we are only allowed to add or subtract K from any element, we can easily infer that mod of all the elements with K should be equal. If it’s not, then return -1 2. sort all the elements of the matrix in non-deceasing order and find the median of the sorted elements 3. The minimum number of steps would occur if we convert all the elements equal to the median
示例
#include <bits/stdc++.h> using namespace std; int getMinOperations(int n, int m, int k, vector<vector<int> >& matrix) { vector<int> arr(n * m, 0); int mod = matrix[0][0] % k; for (int i = 0; i < n; ++i) { for (int j = 0; j < m; ++j) { arr[i * m + j] = matrix[i][j]; if (matrix[i][j] % k != mod) { return -1; } } } sort(arr.begin(), arr.end()); int median = arr[(n * m) / 2]; int minOperations = 0; for (int i = 0; i < n * m; ++i) minOperations += abs(arr[i] - median) / k; if ((n * m) % 2 == 0) { int newMedian = arr[(n * m) / 2]; int newMinOperations = 0; for (int i = 0; i < n * m; ++i) newMinOperations += abs(arr[i] - newMedian) / k; minOperations = min(minOperations, newMinOperations); } return minOperations; } int main() { vector<vector<int> > matrix = { { 2, 4}, { 20, 40}, }; int n = matrix.size(); int m = matrix[0].size(); int k = 2; cout << "Minimum required operations = " << getMinOperations(n, m, k, matrix) << endl; return 0; }
当你编译并执行以上程序时。它会生成以下输出
输出
Minimum required operations = 27
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