Question

#include <iostream>
#include <vector>

using namespace std;

class Solution {
public:
vector<int> smallerNumbersThanCurrent(vector<int>& nums) {

int N = nums.size();
vector<int> result;
vector<int> a(101);
vector<int> b(101);

for (int i = 0; i < N; i++) {
a[nums[i]]++; // what does this mean?
}
for (int i = 1; i < 101; i++) {
b[i] = a[i - 1] + b[i - 1];
}
for (int i = 0; i < N; i++) {
result.push_back(b[nums[i]]);
}
for (int i = 0; i < N; i++)
{
cout << result[i] << " ";
}
return result;
}
};

int main()
{
Solution solution;
vector<int> vect = { 8,1,2,2,3 };
solution.smallerNumbersThanCurrent(vect);
return 0;
}

what does this line mean? a[nums[i]]++;
is there any example or other way to write that?

Answer 1

Answer:

we can write a[num[i]]++ as

a[num[i]] = a[num[i]] + 1;

num[i] return the value from vector num at ith position then this value is taken as the index value for the vector a and at this index, lets say we get value of num[i] = k, then  value at a[k] will be incremented by one.

Note: Let me know if you have any doubt.