LeetCode 821. Shortest Distance to a Character

821. Shortest Distance to a Character 

Given a string S and a character C, return an array of integers representing the shortest distance from the character C in the string.

Example 1:

Input: S = "loveleetcode", C = 'e'
Output: [3, 2, 1, 0, 1, 0, 0, 1, 2, 2, 1, 0]

Note:

1. S string length is in [1, 10000].
2. C is a single character, and guaranteed to be in string S.
3. All letters in S and C are lowercase.

这道题要求给定字符串中每个字符和字符串中某个特定字符C的最小距离，题目不是很难，但是要仔细分析，我的思路是从头到尾遍历字符串，对于每一个字符，都分别向前向后遍历，分别比较两个方向上与字符C的距离，取最小值，最好时间复杂度为O(N)，最差为O(N^2)

class Solution {
public:
    vector<int> shortestToChar(string S, char C) {
        vector<int> res;
        for (int i = 0; i < S.size(); i++)
        {
            int k = i;
            int dis = INT_MAX;
            while (k >= 0)
            {
                if (S[k] == C)
                {
                    dis = min(dis, i - k);
                    break;
                }
                k--;
            }
            k = i;
            while (k <= S.size() - 1)
            {
                if (S[k] == C)
                {
                    dis = min(dis, k - i);
                    break;
                }
                k++;
            }
            res.push_back(dis);
        }
        return res;
    }
};