packagemedium;

publicclassArithmeticSlices {

publicintnumberOfArithmeticSlices(int[]A) {

intsum =0,len =2;

for (inti =2;i <A.length;i++){

if (A[i] -A[i-1] ==A[i-1] -A[i-2]){

len++;

}else {

if (len >2)sum +=calculateSlices(len);

len =2;//reset it to 2

}

}

if(len >2)sum +=calculateSlices(len);

returnsum;

}

intcalculateSlices(intlen){

return (len-1)*(len-2)/2;

}

classSolution2{

publicintnumberOfArithmeticSlices(int[]A) {

intsum =0,curr =0;

for (inti =2;i <A.length;i++){

if (A[i] -A[i-1] ==A[i-1] -A[i-2]){

curr++;

sum +=curr;

}else {

curr =0;

}

}

returnsum;

}

}

}

|419|[Battleships in a Board](https://leetcode.com/problems/battleships-in-a-board/)|[Solution](../../blob/master/MEDIUM/src/medium/BattleshipsinaBoard.java) | O(n^2) |O(1) | Medium| DFS

|417|[Pacific Atlantic Water Flow](https://leetcode.com/problems/pacific-atlantic-water-flow/)|[Solution](../../blob/master/MEDIUM/src/medium/PacificAtlanticWaterFlow.java) | O(m*n*Max(m,n)) |O(m*n) | Medium| DFS

|415|[Add Strings](https://leetcode.com/problems/add-strings/)|[Solution](../../blob/master/EASY/src/easy/AddStrings.java)| O(n)|O(1)| Easy|

|413|[Arithmetic Slices](https://leetcode.com/problems/arithmetic-slices/)|[Solution](../../blob/master/MEDIUM/src/medium/ArithmeticSlices.java) | O(n) |O(1) | Medium| DP

|412|[Fizz Buzz](https://leetcode.com/problems/fizz-buzz/)|[Solution](../../blob/master/EASY/src/easy/FizzBuzz.java)| O(n)|O(1)| Easy|

|404|[Sum of Left Leaves](https://leetcode.com/problems/sum-of-left-leaves/)|[Solution](../../blob/master/EASY/src/easy/SumofLeftLeaves.java)| O(n)|O(h)| Easy|

|398|[Random Pick Index](https://leetcode.com/problems/random-pick-index/)|[Solution](../../blob/master/MEDIUM/src/medium/RandomPickIndex.java) | | | Medium| Reservoir Sampling