36 lines
737 B
C++
36 lines
737 B
C++
class Solution {
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public:
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const static long long MOD = 1000000007;
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int uniqueLetterString(string S) {
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map<char, vector<int>> mp;
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long long cnt = 0;
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int slen = S.size();
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for (int i = 0; i < slen; i++)
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{
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auto iter = mp.find(S[i]);
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if (iter == mp.end())
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{
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tie(iter, ignore) = mp.insert(make_pair(S[i], vector<int>{-1}));
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}
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else
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{
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int sz = iter->second.size();
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int k = iter->second[sz - 2];
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int j = iter->second[sz - 1];
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cnt = (cnt + (j - k)*(i - j)) % MOD;
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}
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iter->second.push_back(i);
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}
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for (const auto& pr : mp)
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{
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int sz = pr.second.size();
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int k = pr.second[sz - 2];
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int j = pr.second[sz - 1];
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cnt = (cnt + (j - k)*(slen - j)) % MOD;
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}
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return cnt;
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}
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};
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