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564.cpp
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564.cpp
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class Solution {
public:
string nearestPalindromic(string n) {
int size = n.size();
long long num = stoll(n);
unordered_set<long long> st;
st.insert(pow(10, size) + 1);
st.insert(pow(10, size - 1) - 1);
if (size & 1) {
string half = n.substr(0, size / 2 + 1);
long long prefix = stoll(half);
for (int i = -1; i <= 1; ++i) {
string prefixNew = to_string(prefix + i);
string rev = prefixNew.substr(0, prefixNew.size() - 1);
reverse(rev.begin(), rev.end());
string temp = prefixNew + rev;
st.insert(stoll(temp));
}
}
else {
string half = n.substr(0, size / 2);
long long prefix = stoll(half);
for (int i = -1; i <= 1; ++i) {
string prefixNew = to_string(prefix + i);
string rev = prefixNew;
reverse(rev.begin(), rev.end());
string temp = prefixNew + rev;
st.insert(stoll(temp));
}
}
long long minDiff = LLONG_MAX;
string res;
for (auto& value : st) {
if (value == num) continue;
if (abs(num - value) < minDiff) {
minDiff = abs(num - value);
res = to_string(value);
}
else if (abs(num - value) == minDiff) {
long long temp = stoll(res);
if (value < temp) res = to_string(value);
}
}
return res;
}
};