Given a number represented as an array of digits, plus one to the number. http://leetcode.com/onlinejudge#question_66

leetcode_plus_one.cpp

class Solution {
public:
    vector<int> plusOne(vector<int> &digits) {
        int all9 = 1;
        for (int i = 0; i < digits.size(); ++i)
            if (digits[i] != 9) {
                all9 = 0;
                break;
            }
        int len = digits.size() + all9;
        vector<int> ret;
        ret.resize(len);
        int cur = len - 1;
        digits[ digits.size() - 1 ]++;
        for (int i = digits.size() - 1; i >= 0; --i) {
            if (digits[i] < 10)
                ret[cur--] = digits[i];
            else {
                ret[cur--] = digits[i] - 10;
                if (i == 0)
                    ret[cur] = 1;
                else
                    digits[i - 1]++;
            }
        }
        return ret;
    }
};