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L394.java
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L394.java
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package Algorithm;
import java.util.Stack;
public class L394 {
/*
* 用栈来解决,每次遇到“[”就把"["之前的res塞进stack里
* 遇到数字就把数字塞进numStack,每次遇到"]"就把stack.pop()
* 和numStack.pop()个res连起来,然后作为新的res,等待下次被
* 塞进栈里面,或者被和stack里的元素连接起来,最后返回res即可
*/
String decodeString(String s) {
int len = s.length();
if(len == 0 || s == null)
return "";
Stack<Integer> numStack = new Stack<Integer>();
Stack<String> strStack = new Stack<String>();
StringBuilder res = new StringBuilder();
for(int i = 0; i < len; i ++) {
char c = s.charAt(i);
if(c == '[') {
strStack.push(res.toString());
res = new StringBuilder();
}else if (c == ']') {
int num = numStack.pop();
StringBuilder temp = new StringBuilder(strStack.pop());
for(int j = 0; j < num; j ++) {
temp.append(res);
}
res = temp;
}else if(Character.isDigit(c)) {
int num = 0;
while(i < len && Character.isDigit(s.charAt(i))) {
num = num * 10 + s.charAt(i) - '0';
i ++;
}
i --;
numStack.push(num);
}else {
res.append(c);
}
}
return res.toString();
}
}