c++ - Unique list of structure -


i have list of following structure 

struct element {    int id;    int groupid;    };

i want know how many unique groups there

for example 

 list<element> myelements;   element e;   e.id = 0;   e.groupid = 2;   myelements.push_back(e);    e.id = 1;   e.groupid = 0;   myelements.push_back(e);    e.id = 2;   e.groupid = 2;   myelements.push_back(e);    e.id = 3;   e.groupid = 1;   myelements.push_back(e);

there 4 elements here 3 unique group ids 0, 1, 2

i'm trying efficient way because list grows in size.

i tried 

struct groupid_unique {   bool operator() (element first, element second)     { return (first.groupid != second.groupid); }      };      myelements.unique(groupid_unique());

but returns me 2 un-repetitive ids 0,1

use set store items (temporarily). set store unique items. size of set number of unique items.

add equality comparator object:

struct element {   bool operator==(element const& rhs) const {     return id == rhs.id && groupid == rhs.groupid;   } };

use set.

std::set<element> elementset{elementlist.begin(), elementlist.end()}; size_t const numuniqueelements = elementset.size();

note there cost (time , space complexity) in constructing set. if want keep repetitions other purpose, can continue list otherwise can switch list , set have unique count readily available (through .size())


Comments

Post a Comment

Popular posts from this blog

python Tkinter Capturing keyboard events save as one single string -

is possible store keyboard events 1 string? code below stores 1 char , prints it. card reader or bar code reader, contains collection of character/ string not 1 character @ time. goal save char pressed text variable. from tkinter import * root = tk() def key(event): text= event.char text+= event.char print ("pressed", text) def callback(event): frame.focus_set() print ("clicked at", event.x, event.y) frame = frame(root, width=100, height=100) frame.bind("<key>", key) frame.bind("<button-1>", callback) frame.pack() root.mainloop() currently, creating text variable , everytime key() function gets called, , text stores last character typed. you can define text module level variable , , use module level text inside key function - text = '' def key(event): global text text+= event.char print("pressed", text)
Read more

android - InAppBilling registering BroadcastReceiver in AndroidManifest -

i'm implementing inapp billing in android app. works well, however, i'm trying decouple broadcast receiver activity manifest. suggestion in android's trivialdrive sample: // important: dynamically register broadcast messages updated purchases. // register receiver here instead of <receiver> in manifest // because call getpurchases() @ startup, therefore can ignore // broadcasts sent while app isn't running. // note: registering listener in activity bad idea, done here // because sample. regardless, receiver must registered after // iabhelper setup, before first call getpurchases(). currently there's class extends broadcastreceiver : public class iabbroadcastreceiver extends broadcastreceiver { /** * intent action receiver should filter for. */ public static final string action = "com.android.vending.billing.purchases_updated"; private final iabbroadcastlistener mlistener; public iabbroadcastreceiver(iabbroadcastlistener listener) { m
Read more

javascript - Z-index in d3.js -

i have map , when hover effect on region of map below yellow line , circle, last ones disappear. how can solve problem? http://jsfiddle.net/ot21n9qx/ var arc = g.append("path") .style("fill", "none") .style("stroke", "yellow") .style("stroke-width", 2) .attr("d", "m" + pathorigin[0] + "," + pathorigin[1] + " q" + svgpoint[0] + "," + pathorigin[1] + " " + svgpoint[0] + "," + svgpoint[1]); var circlesize = d3.scale.linear() .domain([0, 0.5, 1]) .range([4, 10, 4]); svg not have z order draws objects in order created. need create path , circle after create highlight regions. here forked fiddle: http://jsfiddle.net/o00fzgaf/1/
Read more