942. DI String Match

題目原文

Given a string S that only contains "I" (increase) or "D" (decrease), let N = S.length.

Return any permutation A of [0, 1, ..., N] such that for all i = 0, ..., N-1:

• If S[i] == "I", then A[i] < A[i+1]

• If S[i] == "D", then A[i] > A[i+1]

Example 1:

Input: "IDID"
Output: [0,4,1,3,2]

Example 2:

Input: "III"
Output: [0,1,2,3]

Example 3:

Input: "DDI"
Output: [3,2,0,1]

解題思路

1. 遇到I從最小值開始遞增。

2. 遇到D從最大值開始遞減。

程式解答

class Solution 
{
public:
    vector<int> diStringMatch(string S) 
    {
        int N = S.length();
        int lo = 0;
        int hi = N;
        vector<int> ans;
        
        for (int i = 0; i < N; i++)
        {
            if(S[i] == 'I')
            {  
                ans.push_back(lo++);
            }
            else
            {
                ans.push_back(hi--);
            }
        }
        ans.push_back(lo);
        return ans;
    }
};