leetcode Plus ONE

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

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

分析：这是一个进位加法运算，设置进位变量add，初始值1，判断最低位加1后是否满10，满10则add=1，否则=0；如此循环。直至结束：

    vector<int> plusOne(vector<int>& digits) {        int i;int sum=0;int add=1;vector<int>a(digits.size(),0);for(i=digits.size()-1;i>=0;i--){sum=digits[i]+add;add=sum/10;a[i]=sum%10;}if(add==1)a.insert(a.begin(),add);return a;    }