# [LeetCode]#942. DI String Match

1 min readMay 10, 2020

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Environment: Python 3.7

Key technique: append function

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]`

Analysis:

1. Set low=0 and high is 4 based on S.
2. If S[i] is “I”, add low to ans list and low add 1.
3. If S[i] is “D”, add high to ans list and high decrease 1.
4. The last list you can add low and high are OK.

Solution:

`class Solution:    def diStringMatch(self, S):        low,high=0,len(S)        ans=[]        for i in S:            if i=="I":                ans.append(low)                low+=1            else:                ans.append(high)                high-=1        return ans +[low]`

Submissions:

Reference:

https://leetcode.com/problems/di-string-match/solution/