Question

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]

Difficulty:Easy

Category:Math

Analyze

Solution

class Solution {
 public:
  vector<int> diStringMatch(string S) {
    const int n = S.length();
    vector<int> ans(n + 1, INT_MIN);
    int h = n, l = 0;
    for (int i = 0; i < n; i++) S[i] == 'I' ? ans[i] = l++ : ans[i] = h--;
    ans[n] = h;
    return ans;
  }
};

适当进行一些优化:

class Solution {
 public:
  vector<int> diStringMatch(string S) {
    const int n = S.length();
    vector<int> ans;
    ans.reserve(n+1);
    int h = n, l = 0;
    for (int i = 0; i < n; i++) S[i] == 'I' ? ans.emplace_back(l++) : ans.emplace_back(h--);
    ans.emplace_back(h);
    return ans;
  }
};
By guozetang            Updated: 2020-09-19 13:02:30

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