Pairs in an array that sum to 15…
Messy and hacky, should use set rather than map. In reality should use a hash…
#include
#include
Select a random line from a file in a single pass
#include <iostream>
#include <string>
#include <fstream>
#include <stdlib.h>
#include <vector>
using namespace std;
void getrandline(string filename,size_t &selected_line_no,string &selected_line) {
ifstream file(filename.c_str());
selected_line_no = 0;
for(size_t n=1;!file.eof();n++) {
string current_line;
getline(file,current_line);
if(file.eof()) break;
if(rand()%n == 0) { selected_line = current_line; selected_line_no = n-1; }
}
}
int main(int argc,char **argv) {
srand(time(NULL));
vector<size_t> count(100,0); // just for testing, 100 should be > size of the file...
for(size_t n=0;n<100000;n++) {
size_t linenum;
string line;
getrandline(argv[1],linenum,line);
count[linenum]++;
cout << linenum << " " << line << endl;
}
for(size_t n=0;n<count.size();n++) {
cout << n << " " << count[n] << endl;
}
}
Removing things that occur once only from an array
I wonder if there is a better way…
#include <iostream>
#include <string>
#include <vector>
#include <map>
using namespace std;
void remonce(vector<int> &array) {
map<int,int> counts;
for(size_t n=0;n<array.size();n++) {
counts[array[n]]++;
}
vector<int> newarray;
for(size_t n=0;n<array.size();n++) {
if(counts[array[n]] != 1) {
newarray.push_back(array[n]);
}
}
array = newarray;
}
int main() {
vector<int> array;
array.push_back(4);
array.push_back(4);
array.push_back(3);
array.push_back(3);
array.push_back(8);
array.push_back(16);
array.push_back(8);
remonce(array);
for(size_t n=0;n<array.size();n++) {
cout << array[n] << endl;
}
}
Check if string palindrome
#include <iostream>
#include <string>
using namespace std;
bool check(string palendrome) {
size_t limit=0;
if(palendrome.size()%2 == 0) limit = palendrome.size()/2;
else limit = (palendrome.size()-1)/2;
for(size_t n=0;n<limit;n++) {
if(palendrome[n] != palendrome[palendrome.size()-n-1]) return false;
}
return true;
}
int main() {
string palendrome1 = "catac";
bool check1 = check(palendrome1); if(check1 == true) cout << palendrome1 << " is palendromic" << endl; else cout << palendrome1 << " is not palendromic" << endl;
string palendrome2 = "caac";
bool check2 = check(palendrome2); if(check2 == true) cout << palendrome2 << " is palendromic" << endl; else cout << palendrome2 << " is not palendromic" << endl;
string palendrome3 = "zcaacr";
bool check3 = check(palendrome3); if(check3 == true) cout << palendrome3 << " is palendromic" << endl; else cout << palendrome3 << " is not palendromic" << endl;
}
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