递归向量中的最小正数 [英] Smallest positive number in a vector recursively
问题描述
我正在编写一个函数,该函数应该递归地找到给定整数向量中的最小正数.
I'm writing a function that is supposed to recursively find the smallest positive number in a give vector of ints.
现在我的代码是这样的:
Right now my code looks like this:
#include <vector>
using namespace std;
int rec_min_pos(const vector<int> & nums, int size) {
if (size < 1) {
return -1;
} else {
int min = rec_min_pos(nums, size - 1);
if(min < 0){
if(nums[size - 1] <= 0){
return -1;
}else{
return nums[size-1];
}
}else {
if (min < nums[size - 1]) {
return min;
} else {
return nums[size - 1];
}
}
}
}
int main(){
vector<int> nums = {2, -3, 6, -21, 10, -80, 8};
cout << rec_min_post(nums, nums.size());
}
如果我运行这个,我得到 8
,这大概是因为下一个元素是负数.
If I run this, I get 8
, which is presumably because the next element is negative.
之前的版本:
#include <vector>
using namespace std;
int rec_min_pos(const vector<int> & nums, int size) {
if (size < 1) {
return -1;
} else {
int min = rec_min_pos(nums, size - 1);
if (min < nums[size - 1]) {
return min;
} else {
return nums[size - 1];
}
}
}
int main(){
vector<int> nums = {2, -3, 6, -21, 10, -80, 8};
cout << rec_min_post(nums, nums.size());
}
我会得到 -80
这实际上是最小值,但我需要最小的正值.
I would get -80
which is in fact the smallest value, but I need the smallest positive value.
如何从整数向量中得到最小的正值?
What can I do to get the smallest positive value from the integer vector?
推荐答案
def SPN(nums, s):
if s == 0:
# Empty array
return +∞
if nums[s-1] > 0:
# num[s] is admissible, recurse and keep the smallest
return min(nums[s-1], SPN(nums, s-1))
else:
# Just recurse
return SPN(nums, s-1)
print SPN(nums, len(nums)
C++ 版本:
#include <vector>
using namespace std;
int rec_min_pos(const vector<int> & nums, int size) {
if (size < 1) {
return INT_MAX;
}
if(nums[size-1] > 0){
return min(nums[size-1], rec_min_pos(nums, size-1));
}
else{
return rec_min_pos(nums, size-1);
}
}
<小时>
更新:
假设不允许保留 INT_MAX
表示 +∞,我们可以使用负数代替,例如 -1
,约定为 min(x,-1) = x
.
Assuming that reserving INT_MAX
is not allowed to represent +∞, we can use a negative instead, say -1
, with the convention that min(x,-1) = x
.
Infty= -1 # Conventional +∞
def Min(a, b):
if b == Infty:
return a
else:
return min(a, b)
def SPN(nums, s):
if s == 0:
# Empty array
return Infty
if nums[s-1] > 0:
# num[s] is admissible, recurse and keep the smallest
return Min(nums[s-1], SPN(nums, s-1))
else:
# Just recurse
return SPN(nums, s-1)
如果我们使用任何负值表示 +∞ 的约定,这将导致我们得到一个更优雅的版本:
That leads us to a more elegant version if we use the convention that any negative value represents +∞:
def Min(a, b):
if a < 0:
return b
if b < 0:
return a
return min(a, b)
def SPN(nums, s):
if s == 1:
return nums[0] # Assumes len(nums) > 0
return Min(nums[s-1], SPN(nums, s-1))
优雅的 C++ 版本:
Elegant version in C++:
#include <vector>
using namespace std;
int minimum(int a, int b){
if(a < 0){
return b;
}
if(b < 0){
return a;
}
return min(a, b);
}
int SPN(vector<int> nums, int size){
if(size == 1){
return nums[0];
}
return minimum(nums[size-1], SPN(nums, size-1));
}
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