Nearest smaller numbers on left side

Problem: Given an array of integers, find the nearest smaller number for every integer on its left side.

Solution: Use stack.

Implementation:

void printNearestSmaller(int arr[], int len)
{
if(len <= 0)
return;

std::stack<int> st;
for(int i = 0; i < len; ++i)
{
while(!st.empty() && st.top() >= arr[i])
st.pop();

if(st.empty())
std::cout<<"-\t";
else
std::cout<<st.top()<<'\t';
st.push(arr[i]);
}
std::cout<<std::endl;
}

Complexity: O(n)