| 522|[Longest Uncommon Subsequence II](https://leetcode.com/problems/longest-uncommon-subsequence-ii/)|[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_522.java)|| Medium|

| 521|[Longest Uncommon Subsequence I](https://leetcode.com/problems/longest-uncommon-subsequence-i/)|[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_521.java)|| Easy|

| 520|[Detect Capital](https://leetcode.com/problems/detect-capital/)|[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_520.java)|| Easy|

| 519 |[Random Flip Matrix](https://leetcode.com/problems/random-flip-matrix/) |[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_519.java) | | Medium |HashTable, Math, Randomized, Reservoir Sampling

| 518 |[Coin Change 2](https://leetcode.com/problems/coin-change-2/) |[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_518.java) | | Medium | Array, DP

| 517 |[Super Washing Machines](https://leetcode.com/problems/super-washing-machines/) |[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_517.java) | | Hard | DP

| 516 |[Longest Palindromic Subsequence](https://leetcode.com/problems/longest-palindromic-subsequence/) |[Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_516.java) | | Medium | DP

packagecom.fishercoder.solutions.firstthousand;

importjava.util.HashSet;

importjava.util.Random;

importjava.util.Set;

publicclass_519 {

publicstaticclassSolution {

privateintm;

privateintn;

privateSet<Integer>flipped;

privateRandomrandom;

publicSolution(intm,intn) {

this.m =m;

this.n =n;

this.random =newRandom();

this.flipped =newHashSet<>();

}

publicint[]flip() {

inti =random.nextInt(m);

intj =random.nextInt(n);

while (!flipped.add(i *n +j)) {

i =random.nextInt(m);

j =random.nextInt(n);

}

returnnewint[]{i,j};

}

publicvoidreset() {

this.flipped =newHashSet<>();

}

}

}

packagecom.fishercoder.firstthousand;

importcom.fishercoder.common.utils.CommonUtils;

importcom.fishercoder.solutions.firstthousand._519;

importorg.junit.jupiter.api.Test;

publicclass_519Test {

privatestatic_519.Solutionsolution1;

publicvoidtest1() {

solution1 =new_519.Solution(3,1);

CommonUtils.printArray(solution1.flip());

CommonUtils.printArray(solution1.flip());

CommonUtils.printArray(solution1.flip());

solution1.reset();

CommonUtils.printArray(solution1.flip());

}

}