coding-Interview/DecodeString.java at master · arjunmullick/coding-Interview · GitHub

41 lines (35 loc) · 1.33 KB

public class DecodeString {

//https://leetcode.com/problems/decode-string/

class Solution {

public String decodeString(String s) {

Deque<Integer> numStack = new ArrayDeque<>();

Deque<String> strStack = new ArrayDeque<>();

StringBuilder tail = new StringBuilder();

int n = s.length();

for (int i = 0; i < n; i++) {

char c = s.charAt(i);

if (Character.isDigit(c)) {

int num = c - '0';

while (i + 1 < n && Character.isDigit(s.charAt(i + 1))) {

num = num * 10 + s.charAt(i + 1) - '0';

i++;

}

numStack.push(num);

} else if (c == '[') {

strStack.push(tail.toString());

tail = new StringBuilder();

} else if (c == ']') {

StringBuilder tmp = new StringBuilder(strStack.pop());

int repeatedTimes = numStack.pop();

for (int j = 0; j < repeatedTimes; j++) {

tmp.append(tail);

}

tail = tmp;

} else {

tail.append(c);

}

return tail.toString();

}

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