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Pascal's Triangle II in C++
Suppose we have a non-negative index k where k ≤ 33, we have to find the kth index row of Pascal's triangle.
So, if the input is like 3, then the output will be [1,3,3,1]
To solve this, we will follow these steps −
Define an array pascal of size rowIndex + 1 and fill this with 0
for initialize r := 0, when r <= rowIndex, update (increase r by 1), do −
pascal[r] := 1, prev := 1
for initialize i := 1, when i < r, update (increase i by 1), do −
cur := pascal[i]
pascal[i] := pascal[i] + prev
prev := cur
return pascal
Example
Let us see the following implementation to get better understanding −
#include <bits/stdc++.h>
using namespace std;
void print_vector(vector<auto> v){
cout << "[";
for(int i = 0; i<v.size(); i++){
cout << v[i] << ", ";
}
cout << "]"<<endl;
}
class Solution {
public:
vector<int> getRow(int rowIndex) {
vector<int> pascal(rowIndex + 1, 0);
int prev, cur, r, i;
for (r = 0; r <= rowIndex; r++) {
pascal[r] = prev = 1;
for (i = 1; i < r; i++) {
cur = pascal[i];
pascal[i] += prev;
prev = cur;
}
}
return pascal;
}
};
main(){
Solution ob;
print_vector(ob.getRow(3));
}Input
3
Output
[1, 3, 3, 1, ]
Updated on: 10-Jun-2020
196 Views
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