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_22.java
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_22.java
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package com.fishercoder.solutions;
import java.util.ArrayList;
import java.util.List;
public class _22 {
public static class Solution1 {
public List<String> generateParenthesis(int n) {
List<String> result = new ArrayList();
backtrack(result, "", 0, 0, n);
return result;
}
void backtrack(List<String> result, String str, int left, int right, int max) {
if (str.length() == max * 2) {
result.add(str);
return;
}
if (left < max) {
backtrack(result, str + "(", left + 1, right, max);
}
if (right < left) {
backtrack(result, str + ")", left, right + 1, max);
}
}
}
public static class Solution2 {
public List<String> generateParenthesis(int n) {
List<String> result = new ArrayList();
if (n == 0) {
return result;
}
backtrack(result, "", n, n);
return result;
}
void backtrack(List<String> result, String parenthesis, int left, int right) {
if (left > 0) {
backtrack(result, parenthesis + "(", left - 1, right);
}
if (right > left) {
backtrack(result, parenthesis + ")", left, right - 1);
}
if (right == 0) {
result.add(parenthesis);
}
}
}
}