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#52 N-Queens II.cpp
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#52 N-Queens II.cpp
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class Solution {
public:
int totalNQueens(int n) {
return solveNQueens(n).size();
}
vector<vector<string>> solveNQueens(int n) {
vector<vector<string>> collection;
vector<string> conf(n, string(n, '.'));
solveRow(conf, 0, collection);
for(auto& conf : collection) {
for(auto& row : conf) {
std::replace(row.begin(), row.end(), '*', '.');
}
}
return collection;
}
void solveRow(vector<string> conf, size_t idx, vector<vector<string>>& collection) {
if(idx == conf.size()) {
collection.push_back(conf);
return;
}
for(size_t i = 0; i < conf.size(); ++i) {
if(conf[idx][i] != '*') {
vector<string> newConf = conf;
newConf[idx][i] = 'Q';
for(size_t r = i + 1, d = idx + 1; r < conf.size() && d < conf.size(); ++r, ++d) {
newConf[d][r] = '*';
}
if(i != 0) {
for(size_t l = i - 1, d = idx + 1; d < conf.size(); --l, ++d) {
newConf[d][l] = '*';
if(l == 0) {
break;
}
}
}
for(size_t d = idx + 1; d < conf.size(); ++d) {
newConf[d][i] = '*';
}
solveRow(newConf, idx+1, collection);
}
}
}
};