# Number of Valid Subarrays in C++

C++Server Side ProgrammingProgramming

Suppose we have an array A of integers, we have to find the number of non-empty continuous subarrays that satisfy this condition: The leftmost element of the subarray is not larger than other elements in the subarray.

So, if the input is like [1,4,2,5,3], then the output will be 11, as there are 11 valid subarrays, they are like ,,,,,[1,4],[2,5],[1,4,2],[2,5,3],[1,4,2,5],[1,4,2,5,3].

To solve this, we will follow these steps −

• ret := 0

• n := size of nums

• Define one stack st

• for initialize i := 0, when i < size of nums, update (increase i by 1), do −

• x := nums[i]

• while (not st is empty and x < top element of st), do −

• delete element from st

• insert x into st

• ret := size of st + ret

• return ret

Let us see the following implementation to get better understanding −

## Example

Live Demo

#include <bits/stdc++.h>
using namespace std;
class Solution {
public:
int validSubarrays(vector<int>& nums) {
int ret = 0;
int n = nums.size();
stack <int> st;
for(int i = 0; i < nums.size(); i++){
int x = nums[i];
while(!st.empty() && x < st.top()) st.pop();
st.push(x);
ret += st.size();
}
return ret;
}
};
main(){
Solution ob;
vector<int> v = {1,4,2,5,3};
cout << (ob.validSubarrays(v));
}

## Input

{1,4,2,5,3}

## Output

11