PROBLEM DESCRIPTION
Given an integer array A of size N. You have to delete one element such that the GCD(Greatest common divisor) of the remaining array is maximum. Find the maximum value of GCD.
SOLUTION
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public class Solution {
public int solve(int[] A) {
int n = A.length;
//prefix array from L-R using GCD
int[] pfl = new int[n];
//suffix array from R-L using GCD
int[] pfr = new int[n];
//init
pfl[0] = A[0];
pfr[n-1] = A[n-1];
for(int i=1; i<n; i++){
pfl[i] = gcd(pfl[i-1], A[i]);
}
for(int i=n-2; i>=0; i--){
pfr[i] = gcd(pfr[i+1], A[i]);
}
//ans
int max = 1;
//If we remove element at index i, the GCD for remaining elements will be:
//GCD of (GCD of elements from [0, i-1], GCD of elements from [i+1, n-1])
//= GCD of (pfl[i-1], pfr[i+1])
for(int i=1; i<=n-2; i++){
max = Math.max(max, gcd(pfl[i-1], pfr[i+1]));
}
//If we remove the first element, GCD = pfr[1]
max = Math.max(max, pfr[1]);
//If we remove the last element, GCD = pfl[n-2]
max = Math.max(max, pfl[n-2]);
return max;
}
//gcd of a and b
public int gcd(int a, int b){
if(b == 0) return a;
return gcd(b, a%b);
}
}