Date : 8 November 2020

# Aptitude

Out of the total production of iron from hematite, an ore of iron, 20% of the ore gets wasted, and out of the remaining iron, only 25% is pure iron. If the pure iron obtained in a year from a mine of hematite is 80,000kg, then what will be the quantity of hematite mined in the year.

1. 5,00,000 Kg.

2. 4,00,000 Kg.

3. 4,50,000 Kg.

4. None of these.

Let 100 kg of hematite be obtained then 20% of it gets wasted which means 80 kg of ore remains. Pure iron = 25% of remaining ore = 8025/100 = 20 kg. 20 kg pure Iron is obtained from 100 of hematite. 1 kg pure Iron is obtained from = 100/20 hematite; Then, 80000 kg pure Iron is obtained from = (100/20)80000 = 400000 kg hematite.

So , Option (B) 4,00,000 kg is the right answer

# Technical MCQ

Consider an array of length 5 arr[]={9,7,4,2,1} .What are the steps of insertions done while running insertion sort on the array?

1. 7 9 4 2 1 4 7 9 2 1 2 4 7 9 1 1 2 4 7 9

2. 7 4 2 1 9 4 2 1 9 7 2 1 9 7 4 1 9 4 7 2

3. 9 7 4 1 2 9 7 1 2 4 9 1 2 4 7 1 2 4 7 9

4. None of these.

Ans : 7 9 4 2 1 4 7 9 2 1 2 4 7 9 1 1 2 4 7 9

# Coding Question

Given a string, Your task is to return the largest string, based on dictionary order, that can be obtained by erasing a certain number of characters from the string. For two strings x and y, each consisting of m characters, x is larger than y based on dictionary order, when the first j-1 letters in x and y are equal, where 1<=h<=m but the jth letter in x is larger than the jth letter in y .for example “caa” is larger than “baa”, and “abza” is larger than “abqa”.

`Example : Let the string s, be “baca”. The number of characters to be erased k is 1. There are 4 possible ways of deleting exactly one character from that string “aca”, “bca”,”baa”, and “bac”.Among these strings, “bca” is largest in dictionary order . Thus “bca” is the desired answer.`

Constraints:

1<=n<=10^6

0<=k<n

`string contains only English lowercase letters`

Input Format: The first line contains a single integer k, denoting the number of characters to erase. In the second line, there is a single string s, denoting the string to erase the characters from.

Ouput Format: Output the resultant string.

Solution:

`string Solve(string s){     int i;    set<int> st;    st.insert(0);    for(i=1;i<s.length();i++){        while(st.size()>0 and k>0){            auto it = st.end();            it--;            if(s[*it]<s[i]){                st.erase(*it);                k--;            }            else            break;        }        st.insert(i);    }    while(k>0){        auto it = st.end();        it--;        st.erase(it);        k--;    }    string result="";    for(auto it=st.begin();it!=st.end();it++)    {        result.push_back(s[*it]);    }    return result;    }`