Contains Duplicate III LeetCode solution in C++

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class Solution {
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 public:
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  bool containsNearbyAlmostDuplicate(vector<int> &nums, int indexDiff, int valueDiff) {
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    int i = 0;
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    map<int, int> mp;
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    int n = nums.size();
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    for (int j = 0; j < n; j++) {
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      auto val = mp.lower_bound(nums[j]);
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      if (val != mp.end() and (val->first - nums[j]) <= valueDiff) {
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        return true;
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      }
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      if (val != mp.begin()) {
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        val--;
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        if (abs(val->first - nums[j]) <= valueDiff) {
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          return true;
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        }
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      }
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      mp[nums[j]]++;
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      if ((j - i) == indexDiff) {
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        mp[nums[i]]--;
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        if (mp[nums[i]] == 0) {
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          mp.erase(nums[i]);
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        }
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        i++;
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      }
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    }
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    return false;
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  }
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};