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Problem2.java
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Problem2.java
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// Time Complexity : O(n)
// Space Complexity : O(n)
// Did this code successfully run on Leetcode : Yes
// Any problem you faced while coding this : No
// Your code here along with comments explaining your approach
class Solution {
public String decodeString(String s) {
Stack<Integer> countStack = new Stack<>();
Stack<StringBuilder> stringStack = new Stack<>();
StringBuilder currentString = new StringBuilder();
int k = 0;
for (char c : s.toCharArray()) {
if (Character.isDigit(c)) {
// Build the number k
k = k * 10 + (c - '0');
} else if (c == '[') {
// Push the current number and string onto their stacks
countStack.push(k);
stringStack.push(currentString);
// Reset for the new segment
currentString = new StringBuilder();
k = 0;
} else if (c == ']') {
// Pop the count and the previous string
int count = countStack.pop();
StringBuilder decodedString = stringStack.pop();
// Append the current string count times to the decoded string
for (int i = 0; i < count; i++) {
decodedString.append(currentString);
}
// Set the current string to the decoded string
currentString = decodedString;
} else {
// If it's a character, append it to the current string
currentString.append(c);
}
}
return currentString.toString();
}
}