66. Plus One

1.描述

Given a non-negative integer represented as a non-empty array of digits, plus one to the integer.

You may assume the integer do not contain any leading zero, except the number 0 itself.

The digits are stored such that the most significant digit is at the head of the list.

2.分析

3.代码

/**
 * Return an array of size *returnSize.
 * Note: The returned array must be malloced, assume caller calls free().
 */
int* plusOne(int* digits, int digitsSize, int* returnSize) {
    if (NULL == digits || 0 >= digitsSize) exit(-1);
    
    bool all_digits_are_9 = true;
    for (unsigned int i = 0; i < digitsSize && all_digits_are_9; ++i) {
        if (digits[i] != 9) all_digits_are_9 = false;
    }
    *returnSize = all_digits_are_9 ? digitsSize+1 : digitsSize;
    int *array = (int*)malloc(sizeof(int) * (*returnSize));
    if (NULL == array) exit(-1);
    
    array[*returnSize - 1] = digits[digitsSize - 1] + 1;
    int carry = array[*returnSize - 1] / 10;
    array[*returnSize - 1] = array[*returnSize - 1] % 10;
    for (int i = 1; i < digitsSize; ++i) {
        array[*returnSize - i - 1] = digits[*returnSize - i - 1] + carry;
        carry = array[*returnSize - i - 1] / 10;
        array[*returnSize - i - 1] = array[*returnSize - i - 1] % 10;
    }
    if (carry) array[0] = carry;
    return array;
}