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Algorithms in STL#

#include<algorithm>
#include<vector>
vector<int>v

sort#

// ascending order
sort(v.begin(),v.end());  
// decending order
sort(v.begin(),v.end(),greater<int>());

or

bool comapre(int a,int b)
{
return a>b;
}
// decending order
sort(v.begin(),v.end(),compare);

reverse#

reverse(v.begin(),v.end());

for_each#

//Print every element of vector 
void print(int n)
{
    cout<<n<<" ";
}
for_each(v.begin(),v.end(),print);

or

for_each(v.begin(), v.end(), [](int n){ cout << n << " "; });

max and min#

*max_element(v.begin(),v.end())
*min_element(v.begin(),v.end())

sum#

"numeric" header file for accumulate

accumulate(v.begin(),v.end(),0);

find#

  • n=element want to search
  • return address
// element we want to find
*find(v.begin(),v.end(),n)

// index of the element
find(v.begin(),v.end(),4)-v.begin()

count#

count(v.begin(),v.end(),element)

return true if element is present

if(binnary_search(v.begin(),v.end(),element))
cout<<"present";
else
cout<<"not present";

lower_bound#

return the address of first occurance where the element is present 

lower_bound(v.begin(),v.end(),element);

for returning index

lower_bound(v.begin(),v.end(),element)-v.begin();

upper_bound#

return the address next to the last occurence where the element is present

upper_bound(v.begin(),v.end(),element)-v.begin();

next_permutation#

return value:

  • true : if the function could rearrange the object as a lexicographically greater permutation.
  • false: to indicate that the arrangement is not greater than the previous, but the lowest possible (sorted in ascending order).
 next_permutation(v.begin(),v.end());

prev_permutation#

prev_permutation(v.begin(),v.end());

all_of#

return true if all are positive

bool positive(int n)
{
    return n>0;
}

if(all_of(v.begin(),v.end(),positive))
cout<<"all positive\n";
else
cout<<"at least one negavtive is present\n";

any_of#

return true any of is positive

bool positive(int n)
{
    return n>0;
}

if(any_of(v.begin(),v.end(),positive))
cout<<"Positive is present\n";
else
cout<<"Positive is not present\n";

none_of#

bool positive(int n)
{
    return n>0;
}
if(none_of(var.begin(),var.end(),positive))
cout<<"none of the elemnts is positive\n";
else
cout<<"atleat one of the elemnts is positive ";