#CodingStyle

Coding Style

  1. Leave blank space around each operations
  2. Give meaningful names to parameters
  3. Add space line between two logic blocks

For example, Implement strStr():

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public class Solution {
public String strStr(String haystack, String needle) {
if(haystack.length() < needle.length()) {
return null;
}
if(haystack == null || needle == null || needle.length() == 0) {
return haystack;
}

for(int i = 0; i <= haystack.length() - needle.length(); i++) {
boolean find = true;
for(int j = 0; j < needle.length(); j++) {
if(haystack.charAt(i + j) != needle.charAt(j)) {
find = false;
break;
}
}
if(find == true) {
return haystack.substring(i);
}
}

return null;
}
}

Tips: A well-known algorithm to solve this problem is using KMP. This method can run in O(m+n) time. But usually, during a 45 minutes interview, complete this O(m*n) method is enough. So, understanding what the point the interviewer asks is very important.

Think it in this way. If I were the interview:
This guy may be my potential colleague. Is there any bug here? Because if there are many bugs, I will probably debug a lot for him when we are in a team.
Is he talktive? Well, I will give you limited conditions about the problem and I hope you can ask me for more details. Also, to every question, pay attention to the boundry condition.

When we solve a coding problem

  1. Pay attention to the boundry condition
  2. Do communication during the writing part
  3. When finished coding, do a test case no matter the interviewer request or not

Permutations Problems

Subsets:

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public class Solution {
public ArrayList<ArrayList<Integer>> subsets(int[] S) {
ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();
ArrayList<Integer> subset = new ArrayList<Integer>();
Arrays.sort(S);
helper(result, subset, 0, S);
return result;
}

private void helper(ArrayList<ArrayList<Integer>> result, ArrayList<Integer> subset, int len, int[] S) {
result.add(new ArrayList<Integer>(subset));
for(int i = len; i < S.length; i++) {
subset.add(S[i]);
helper(result, subset,i + 1, S);
subset.remove(subset.size() - 1);
}
}
}

Similar Problems:
SubsetsII
Permutations
PermutationsII
CombinationSum
Letter Combination of a Phone Number
Palindrome Partitioning
Restore IP address

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