algorithm - Implement a queue in which push_rear(), pop_front() and get_min() are all constant time operations -


i came across question: implement queue in push_rear(), pop_front() , get_min() constant time operations.

i thought of using min-heap data structure has o(1) complexity get_min(). push_rear() , pop_front() o(log(n)).

does know best way implement such queue has o(1) push(), pop() , min()?

i googled this, , wanted point out algorithm geeks thread. seems none of solutions follow constant time rule 3 methods: push(), pop() , min().

thanks suggestions.

you can implement stack o(1) pop(), push() , get_min(): store current minimum each element. so, example, stack [4,2,5,1] (1 on top) becomes [(4,4), (2,2), (5,2), (1,1)].

then can use 2 stacks implement queue. push 1 stack, pop one; if second stack empty during pop, move elements first stack second one.

e.g pop request, moving elements first stack [(4,4), (2,2), (5,2), (1,1)], second stack [(1,1), (5,1), (2,1), (4,1)]. , return top element second stack.

to find minimum element of queue, @ smallest 2 elements of individual min-stacks, take minimum of 2 values. (of course, there's logic here case 1 of stacks empty, that's not hard work around).

it have o(1) get_min() , push() , amortized o(1) pop().


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