# 942. DI String Match

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]
```

**Note:**

1. `1 <= S.length <= 10000`
2. `S` only contains characters `"I"` or `"D"`.

```cpp
vector<int> diStringMatch(string S) { // time: O(n); space: O(n)
    int n = S.length(), left = 0, right = n;
    vector<int> res(n + 1);
    for (int i = 0; i < n; ++i) {
        res[i] = S[i] == 'I' ? left++ : right--;
    }
    res[n] = left; // either left or right is okay
    return res;
}
```
