修改

Question

我试图从this了解J.F. Sebastian算法，但我尝试编译它（gcc/g++ 4.8）得到一个奇怪的编译器错误：

const int n=101,m=31,k=*16-1;
int i;
srand(time(NULL));
for(i=0;i<n;i++)    x[i]=rand();
std::sort(x,x+m,std::greater<float>());
std::sort(x+m,x+n,std::greater<float>());
float v=nsmallest_iter(x,x+m,x+m+1,x+n,n-1-k,std::greater<float>());

修改

添加我得到的-std=c++11标志：

  from blabla.cpp:2:
blabla.cpp: In instantiation of ‘typename std::iterator_traits<_Iterator>::value_type nsmallest_iter(RandomAccessIterator, RandomAccessIterator, RandomAccessIterator, RandomAccessIterator, size_t, Compare) [with RandomAccessIterator = float*; Compare = std::greater<float>; typename std::iterator_traits<_Iterator>::value_type = float; size_t = long unsigned int]’:
blabla.cpp:58:64:   required from here
blabla.cpp:28:66: error: ‘issorted’ was not declared in this scope
  assert(issorted(firsta,lasta,less) && issorted(firstb,lastb,less));
                                                                  ^
blabla.cpp:28:35: error: ‘issorted’ was not declared in this scope, and no declarations were found by argument-dependent lookup at the point of instantiation [-fpermissive]
  assert(issorted(firsta,lasta,less) && issorted(firstb,lastb,less));
                                   ^
blabla.cpp:28:66: note: ‘issorted’ declared here, later in the translation unit
  assert(issorted(firsta,lasta,less) && issorted(firstb,lastb,less));
                                                              ^

有人知道如何解决这个问题吗？

Answer 1

您正在使用C ++ 11功能，因此您必须使用编译标志

-std=c++11

或

-std=c++0x

对于第二个问题，您可能遗漏了一些标题或者代码存在问题。

编辑：issorted可能会引用std::is_sorted。它可以在包含#include <algorithm>

中找到

Answer 2

将issorted替换为std::is_sorted （如果不存在，请添加#include <algorithm>）
（用C ++ 11编译）

排序数组实现的快速kth元素

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2 个答案: