leetcode/problems/src/stack/DecodedStringAtIndex.java at master · KindleBooks66/leetcode · GitHub

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package stack;

import java.util.Stack;

/** Created by gouthamvidyapradhan on 12/05/2019 */

public class DecodedStringAtIndex {

public static void main(String[] args) {

System.out.println(new DecodedStringAtIndex().decodeAtIndex("ha22", 5));

}

class Node {

String S;

long count;

int multiple;

Node(String S, long count, int multiple) {

this.S = S;

this.count = count;

this.multiple = multiple;

}

public String decodeAtIndex(String S, int K) {

Stack<Node> stack = new Stack<>();

StringBuilder sb = new StringBuilder();

char prev = ' ';

for (char c : S.toCharArray()) {

if (Character.isDigit(c)) {

String currStr = sb.toString();

long len = 0L;

if (!stack.isEmpty()) {

len = stack.peek().count * stack.peek().multiple;

}

stack.push(

new Node(currStr, len + (currStr.length()), Integer.parseInt(String.valueOf(c))));

if (((len + (currStr.length())) * Integer.parseInt(String.valueOf(c))) >= K) {

break;

}

prev = c;

} else {

if (Character.isDigit(prev)) {

sb = new StringBuilder();

}

sb.append(c);

prev = c;

}

while (!stack.isEmpty()) {

Node top = stack.peek();

long l = top.count;

if (K <= l) {

return String.valueOf(top.S.charAt((int) l - K - 1));

}

long mod = (K % l);

if (mod == 0) {

return String.valueOf(top.S.charAt(top.S.length() - 1));

}

if (l - top.S.length() < mod) {

long i = l - mod;

return String.valueOf(top.S.charAt(top.S.length() - (int) i - 1));

} else {

stack.pop();

}

return "";

}

leetcode/problems/src/stack/DecodedStringAtIndex.java at master · KindleBooks66/leetcode · GitHub

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