Deepeshkumar Deepeshkumar - 18 days ago 5
Java Question

How to solve this (http://codingbat.com/prob/p168357) 'codingbat' example efficiently?

I came across this problem on codingbat.com : Problem

Problem:

Given an array of ints, return true if the array contains two 7's next to each other, or there are two 7's separated by one element, such as with {7, 1, 7}.

has77([1, 7, 7]) → true

has77([1, 7, 1, 7]) → true

has77([1, 7, 1, 1, 7]) → false

I solved it but my approach is not that efficient. The code of my solution is large compared to the problem. Can anybody show me how to solve this problem in a smart way.

My code:

public boolean has77(int[] nums) {
int i = 0;
int arraylength = 0;
while(i != nums.length){
if(nums[i] == 7){
arraylength++;
}
i++;
}
int[] sevens = new int[arraylength];
if(arraylength == 0){
return false;
}
i =0;
int j = 0;
while(i != nums.length){
if(nums[i] == 7){
sevens[j] = i;
j++;
}
i++;
}
i = 0;
while(i != arraylength-1){
if(sevens[i+1] - sevens[i]==1 || (sevens[i+1]- sevens[i]==2)){
return true;
}
i++;
}
return false;
}

Answer

This answer will tell you how to do it, but will not give you the code. Writing the code is for you to do, since you chose at accept the challenge on CodingBat.

More efficiently solution: Only iterate the array once. If current element is a 7, and previous element or the one before it is also a 7, return true.