LeetCode-in-Java

66. Plus One

Easy

You are given a large integer represented as an integer array digits, where each digits[i] is the ith digit of the integer. The digits are ordered from most significant to least significant in left-to-right order. The large integer does not contain any leading 0’s.

Increment the large integer by one and return the resulting array of digits.

Example 1:

Input: digits = [1,2,3]

Output: [1,2,4]

Explanation: The array represents the integer 123. Incrementing by one gives 123 + 1 = 124. Thus, the result should be [1,2,4].

Example 2:

Input: digits = [4,3,2,1]

Output: [4,3,2,2]

Explanation: The array represents the integer 4321. Incrementing by one gives 4321 + 1 = 4322. Thus, the result should be [4,3,2,2].

Example 3:

Input: digits = [0]

Output: [1]

Explanation: The array represents the integer 0. Incrementing by one gives 0 + 1 = 1. Thus, the result should be [1].

Example 4:

Input: digits = [9]

Output: [1,0]

Explanation: The array represents the integer 9. Incrementing by one gives 9 + 1 = 10. Thus, the result should be [1,0].

Constraints:

• 1 <= digits.length <= 100
• 0 <= digits[i] <= 9
• digits does not contain any leading 0’s.

Solution

public class Solution {
    public int[] plusOne(int[] digits) {
        int num = 1;
        int carry = 0;
        int sum;
        for (int i = digits.length - 1; i >= 0; i--) {
            if (i == digits.length - 1) {
                sum = digits[i] + carry + num;
            } else {
                sum = digits[i] + carry;
            }
            carry = sum / 10;
            digits[i] = sum % 10;
        }
        if (carry != 0) {
            int[] ans = new int[digits.length + 1];
            ans[0] = carry;
            System.arraycopy(digits, 0, ans, 1, ans.length - 1);
            return ans;
        }
        return digits;
    }
}

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