找到把一个数字表示为小于它的数字之和的方法数的 C++ 程序
在这个程序中,我们将计算一个数字可以用小于它的数字之和来表示的方法数。此程序将计算给定数字的划分。我们取一个数字 n 作为输入,然后从一个数字开始,每次去掉 1 来分解它。如果生成了新划分,则增加计数器。
算法
partitionCount(n)
输入:数字 n
输出:划分数
Begin Create array p of size n k := 0 count := -1 put n as the first element of array p Repeat the following steps, do increase count by 1 rem := 0 while k >= 0 and p[k] = 1, do rem := rem + p[k] decrease k by 1 done if k < 0, then return count p[k] := p[k] – 1 rem := rem + 1 while rem >= p[k], do p[k+1] := p[k] rem := rem - p[k] increase k by 1 done p[k+1] := rem increase k by 1 done End
示例代码
#include<iostream> using namespace std; int partitionCount(int n){ //used to count all possible partitions int p[n], k = 0, count = -1; p[k] = n; //add n as the first element of array while(true) { //repeat untill all elements are turned to 1 count++; int rem = 0; while (k >= 0 && p[k] == 1){ // Move the pointer to the correct index where p[k] > 1. rem += p[k]; k--; } if (k < 0) // If k < 0 then the all the element are broken down to 1. return count; //otherwise decrease the value by 1, and increase rem p[k]--; rem++; while (rem > p[k]) { // repeat until the number of 1's are greater than the value at k index. p[k+1] = p[k]; rem -= p[k]; // Decrease the rem_val value. k++; } p[k+1] = rem; // Assign remaining value to the index next to k. k++; } } main() { int n, c; cout<<"Enter number for partition counting: "; cin>>n; if (n <= 0) { //n must be greater than or equal to 1 cout<<"Invalid value of n"; exit(1); } c = partitionCount(n); cout<<"The number of partitions: "<<c; }
输出
Enter number for partition counting: 7 The number of partitions: 14
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