Climbing the leaderboard- hacker rank [closed] - c++

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I was solving this problem in Hackerrank.
This question will give us an array of scores. We have to rank those sores as per the dense leader board ranking. It means the highest score gets the first rank, if the next score is equal to the highest rank, we give them the same rank. If it is less than that, we give it the next immediate rank.
ex- the scores 100, 80, 80, 60 will get ranks 1, 2,2 3.
ALso we are given an array of alice's score and we have to find out what rank Alice will get with each of her score.
Note that the scores are given in descending order. And Alice's scores are given in ascending order.
WHat I do is first create an array whoose ith element will denote the rank of ith score in the score vector.
Then I take the smallest score of ALice and do a search of the smallest score >= Alice's score. Then I gave ALice's score the rank accordingly. AFter that I pick the second smallest alice score and this time start searching for the smallest score >= Alice's score from where I left off.
This is the code that I wrote-
#include <vector>
#include <iostream>
using namespace std;
//function for the question.
vector<int> climbingLeaderboard(vector<int> scores, vector<int> alice)
{
vector<int> rank; //another array that will store the rank of all people already on the leaderboard
vector<int> result; //vector that will store the return value of alice's rank.
int val = scores[0]; //stores the current score that we are pointing on.
int len = 1, k, n = 0; //len is the current rank we are on. it changes if value(score) changes.
for (int i = 0; i < scores.size(); i++) {
if (scores[i] == val) { //if the scores are equal...
rank.push_back(len); //it stores the value of len that is the rank. This command ensures that the same scores have the same rank.
}
else if (scores[i] < val) { //if the score is less than val....
len++; //increments len by 1.
rank.push_back(len); //gives the current len as rank to the next person.
val = scores[i]; //sets the new value to the current score
}
}
//now I have stored ranks. Now for giving alice ranks...
k = scores.size() - 1; //points to the current score that we are comparing for Alice.
for (int j = 0; j < alice.size(); j++) { //does the loop for every score of Alice given.
k = n; //sets k=n so that we begin our search with the same index we left on for the next time.
while (k >= 0) {
if (scores[k] < alice[j]) { //if score is less, sub 1 from k
k--;
}
else if (scores[k] == alice[j]) {
result[j] = rank[k]; //if scores are equal, we set the rank of alice same as that of the rank that this score got.
n = k; //we store the value of k for which the scores are equal.
k = -1; //to end the while loop
}
else if (scores[k] > alice[j]) {
result[j] = rank[k] - 1;
n = k; //we do the same if the scores are one less, but give one less rank
k = -1;
}
}
}
return result; //return the vector.
}
// main function just takes in all the values and prints the vector that we get
int main()
{
int n, value, m;
cin >> n;
vector<int> scores;
vector<int> alice;
for (int i = 0; i < n; i++) {
cin >> value;
scores.push_back(value);
}
cin >> m;
for (int i = 0; i < m; i++) {
cin >> value;
alice.push_back(value);
}
vector<int> result;
result = climbingLeaderboard(scores, alice);
for (int k = 0; k < m; k++) {
cout << result[k];
cout << endl;
}
return 0;
}
It is showing a runtime error. Pls look at the code and tell me whats wrong. Also I would suggest to look at the link once bcoz it will explain the question much better than I evr will.
It also contains the sample inputs and sample outputs. The input format is a bit strange.

Answer 1

Looking at the debug output it's clear that you have an out of bounds access on one of your vectors.
Looking at the code I can see at least one such problem (there may be more)
vector<int> result;
...
result[j]=rank[k];
...
result[j]=rank[k]-1;
result is a vector with size 0, at no point do you resize it. So result[j]=... is an out of bounds vector access.