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Java-based LeetCode algorithm problem solutions, regularly updated

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package g1501_1600.s1556_thousand_separator;

// #Easy #String #2022_04_11_Time_1_ms_(57.92%)_Space_41.7_MB_(31.67%)

/**
 * 1556 - Thousand Separator\.
 *
 * Easy
 *
 * Given an integer `n`, add a dot (".") as the thousands separator and return it in string format.
 *
 * **Example 1:**
 *
 * **Input:** n = 987
 *
 * **Output:** "987"
 *
 * **Example 2:**
 *
 * **Input:** n = 1234
 *
 * **Output:** "1.234"
 *
 * **Constraints:**
 *
 * *   0 <= n <= 2³¹ - 1
**/
public class Solution {
    public String thousandSeparator(int n) {
        String str = Integer.toString(n);
        StringBuilder sb = new StringBuilder();
        int i = str.length() - 1;
        int j = 1;
        while (i >= 0) {
            sb.append(str.charAt(i));
            j++;
            if (j % 3 == 0) {
                sb.append(".");
            }
            i--;
            j++;
        }
        String result = sb.reverse().toString();
        if (result.charAt(0) == '.') {
            result = result.substring(1);
        }
        return result;
    }
}