116 lines
2.5 KiB
C++
116 lines
2.5 KiB
C++
/*
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VIM: let b:lcppflags="-std=c++14 -O2 -pthread"
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VIM: let b:wcppflags="/O2 /EHsc /DWIN32"
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VIM-: let b:argv=""
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*/
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#include <iostream>
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#include <exception>
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#include <vector>
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#include <string>
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#include <unordered_map>
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/*
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FB On-site March
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Q: Find number of Islands.
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XXXOO
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OOOXX
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XXOOX
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Return 3 islands.
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1 1 1 O O
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O O O 2 2
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3 3 O O 2
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*/
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int number_of_islands( const std::vector<std::string>& board )
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{
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auto n = board.size();
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auto m = board.front().size();
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std::unordered_map<int,int> g;
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auto idx = [m](size_t i, size_t j){
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return i*m+j;
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};
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auto root = [&g](size_t idx){
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for (; g[idx] != idx; idx = g[idx] );
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return idx;
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};
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for (size_t i = 0; i < n; ++i ){
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for (size_t j = 0; j < m; ++j){
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if (board[i][j] == 'x'){
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if (j>0 && board[i][j-1] == 'x'){
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g[idx(i,j)]=g[idx(i,j-1)];
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if (i>0 && board[i-1][j] == 'x'){
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g[root(idx(i-1,j))]=g[idx(i,j)];
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}
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}
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else if (i>0 && board[i-1][j] == 'x'){
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g[idx(i,j)]=g[idx(i-1,j)];
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}
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else {
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g[idx(i,j)]=idx(i,j);
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}
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}
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}
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}
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int count = 0;
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for ( const auto& node: g){
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if ( node.first == node.second ){
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++count;
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}
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}
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return count;
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}
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int main ( void )
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{try{
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std::cout << number_of_islands({
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"xxxoo",
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"oooxx",
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"xxoox"
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}) << std::endl;
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std::cout << number_of_islands({
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".xx..",
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"xx...",
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"xxxxx"
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}) << std::endl;
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std::cout << number_of_islands({
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"....x",
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"....x",
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"xxxxx"
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}) << std::endl;
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std::cout << number_of_islands({
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"xxxxx",
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"xxxxx",
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"xxxxx"
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}) << std::endl;
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std::cout << number_of_islands({
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"xxxxx",
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"....x",
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"xxx.x",
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"x...x",
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"xxxxx"
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}) << std::endl;
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return 0;
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}
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catch ( const std::exception& e )
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{
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std::cerr << std::endl
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<< "std::exception(\"" << e.what() << "\")." << std::endl;
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return 2;
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}
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catch ( ... )
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{
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std::cerr << std::endl
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<< "unknown exception." << std::endl;
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return 1;
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}}
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