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Java-based LeetCode algorithm problem solutions, regularly updated
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package g0701_0800.s0726_number_of_atoms;
// #Hard #String #Hash_Table #Sorting #Stack #2022_03_24_Time_4_ms_(87.22%)_Space_42.7_MB_(28.23%)
import java.util.ArrayList;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Stack;
@SuppressWarnings({"java:S135", "java:S1149"})
public class Solution {
private boolean isLower(char c) {
return c >= 97 && c <= 122;
}
private boolean isDigit(char c) {
return c >= 48 && c <= 57;
}
public String countOfAtoms(String formula) {
int product = 1;
Stack mlrStack = new Stack<>();
Map count = new HashMap<>();
int i = formula.length() - 1;
while (i >= 0) {
char c = formula.charAt(i);
if (c == '(') {
product /= mlrStack.pop();
i--;
continue;
}
int rank = 1;
int mlr = 0;
while (isDigit(c)) {
mlr += rank * (c - 48);
rank *= 10;
c = formula.charAt(--i);
}
if (mlr == 0) {
++mlr;
}
mlrStack.push(mlr);
product *= mlr;
if (c == ')') {
i--;
continue;
}
StringBuilder atom = new StringBuilder();
while (isLower(c)) {
atom.insert(0, c);
c = formula.charAt(--i);
}
atom.insert(0, c);
String name = atom.toString();
count.put(name, count.getOrDefault(name, 0) + product);
product /= mlrStack.pop();
i--;
}
List atomList = new ArrayList<>(count.keySet());
atomList.sort(Comparator.naturalOrder());
StringBuilder res = new StringBuilder();
for (String atom : atomList) {
res.append(atom);
if (count.get(atom) > 1) {
res.append(count.get(atom));
}
}
return res.toString();
}
}
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