Massive Algorithms: Find a missing number in a string -- Amazon

Str="4142434546" Findout missing no 44.Add it to str;

Output:"414243444546".

public class FindMissingNumInString {

public static boolean ExpectedNextNum(String str, int num, int start) {

if (start + Integer.toString(num).length() > str.length()) {

return false;

}

int expected = Integer.parseInt(

str.substring(start, start + Integer.toString(num).length()));

return (num == expected);

}

public static int FindMissingNum(String str) {

int len = str.length();

int i = 1;

int missingNum = Integer.MIN_VALUE;

while (i <= len / 2) {

int start = i;

int curr = Integer.parseInt(str.substring(0, i));;

boolean result = true;

while (result) {

if (result = ExpectedNextNum(str, curr + 1, start)) {

start += Integer.toString(curr + 1).length();

curr = curr + 1;

} else if (result = ExpectedNextNum(str, curr + 2, start)) {

start += Integer.toString(curr + 2).length();

missingNum = curr + 1;

curr = curr + 2;

}

if (start == len) {

return missingNum;

}

i++;

}

return missingNum;

}

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