Square Root Decomposition to Solve Sum of array elements Range Queries in Competitive Programming

#include<iostream>

#include<cmath>

using namespace std;

int main() {

  int a[] ={1,5,2,4,6,1,3,5,7},n=9;  

  int bs=sqrt(n); //block_size

  int nob=ceil((double)n/bs);//number of blocks

  int res[nob],j=0,sum; //res array stores the block sum

  //printf("%d",nob);

  for(int i=0;i<nob;i++)

  {

      sum=0;

      for(int c=0;c<bs;c++,j++)

        sum=sum+a[j];

      res[i]=sum;  //updating block sum

  }

 //for(int i=0;i<nob;i++)

 //cout<<res[i]<<" ";

  int noq,ad,b_id;

  cin>>noq;

  while(noq--)

  {

      int l,r,opt;

      cin>>opt>>l>>r;

    // l--;r--;     

      switch(opt)

      {

          case 1: b_id=l/bs;

                  res[b_id]=res[b_id]-a[l]+r;

                  a[l]=r;

                  break;

          case 2:  ad=0;

                    while(l<r && l%bs != 0 && l!=0 ){

                        ad=ad+a[l];l++;}

                     while(l+bs-1<=r)

                    {

                        ad=ad+res[l/bs];  //l/bs will give the block index

                        l=l+bs;

                        // cout<<ad<<endl;

                    }

                    for(;l<=r;l++)

                        ad=ad+a[l];

                     cout<<ad<<endl;

      }

 }

  return 0;

}

making a video out of images in matlab

=====================In older versions of MATLAB========================

samples_dir='C:/data'; % data is folder name that has images

files = dir([samples_dir , '\*.jpg']);
aviObj = avifile('C:\test.avi', 'Compression', 'MSVC'); %test.avi is the name of the video and gets stored
%addframe cannot be used for true color images, so convert to gray scale and then add 

%video quality is not good

for i=1:length(files)
f_bmp=[samples_dir '\' files(i).name];
img=imread(f_bmp);
gr=rgb2gray(img);
aviObj = addframe(aviObj, gr);
end
aviObj=close(aviObj);

===================In newer versions of MATLAB===========================
 clear all;
close all;
samples_dir='C:/data'; % data is folder name that has images

Files = dir([samples_dir , '\*.jpg']);

VideoFile='C:\data\MyVideo'; %path of the video file to be saved
writerObj = VideoWriter(VideoFile);
writerObj.FrameRate =1; %increase the frame rate, here i have used 1 frame per second
open(writerObj);
for t= 1:length(Files)
Frame=imread(strcat('C:\data','\',Files(t).name));
writeVideo(writerObj,im2frame(Frame));
end
close(writerObj);

%To play the video

videoFReader = vision.VideoFileReader('C:\data\MyVideo.avi');
videoPlayer = vision.VideoPlayer;
while ~isDone(videoFReader)
   frame = step(videoFReader);
   step(videoPlayer,frame);
end
release(videoFReader);
release(videoPlayer);
                                                  (or)
implay('C:/data/MyVideo.avi');

=============================================================================

Program to read images in a directory as a video

===========================================================================

samples_dir='C:/data'; % data is folder name that has images

files = dir([samples_dir , '\*.jpg']);

hVPlayer=vision.VideoPlayer;
for i=1:length(files)
f_bmp=[samples_dir '\' files(i).name];
img=imread(f_bmp);
step(hVPlayer,img);
end

release(hVPlayer);

====Reading a 'mpg' video inbuilt in MATLAB and displaying the 36th,72nd,108th and 141th frame.======

clear all;
close all;
videobj=mmreader('xylophone.mpg');
numframes=get(videobj,'numberofframes');

x=read(videobj,36);
y=read(videobj,72);
z=read(videobj,108);
k=read(videobj,141);
subplot(221);imshow(x);title('36th frame');
subplot(222);imshow(y);title('72th frame');
subplot(223);imshow(z);title('108th frame');
subplot(224);imshow(k);title('141th frame');

=====================================================================