Flipping Coins
Problem Statement :
There are N coins kept on the table, numbered from 0 to N - 1. Initially, each coin is kept tails up. You have to perform two types of operations: 1) Flip all coins numbered between A and B inclusive. This is represented by the command "0 A B" 2) Answer how many coins numbered between A and B inclusive are heads up. This is represented by the command "1 A B". Input : The first line contains two integers, N and Q. Each of the next Q lines are either of the form "0 A B" or "1 A B" as mentioned above. Output : Output 1 line for each of the queries of the form "1 A B" containing the required answer for the corresponding query. Sample Input : 4 7 1 0 3 0 1 2 1 0 1 1 0 0 0 0 3 1 0 3 1 3 3 Sample Output : 0 1 0 2 1 Constraints : 1 <= N <= 100000 1 <= Q <= 100000 0 <= A <= B <= N - 1
Solution :
Solution in C :
#include <stdio.h>
#include <stdlib.h>
int t[20000002] = { 0 }, lz[20000002] = { 0 };
void update(int node, int s, int e, int l, int r) {
if (lz[node]) {
t[node] = (e - s + 1) - t[node];
if (s != e) {
lz[node << 1] ^= 1;
lz[(node << 1) | 1] ^= 1;
}
lz[node] = 0;
}
if (r < s || e < l || e < s)
return;
else if (l <= s && e <= r) {
t[node] = (e - s + 1) - t[node];
if (s != e) {
lz[node << 1] ^= 1;
lz[(node << 1) | 1] ^= 1;
}
return;
}
int m = s + (e - s) / 2;
update(node << 1, s, m, l, r);
update((node << 1) | 1, m + 1, e, l, r);
t[node] = t[node << 1] + t[(node << 1) | 1];
}
int query(int node, int s, int e, int l, int r) {
if (lz[node]) {
t[node] = (e - s + 1) - t[node];
if (s != e) {
lz[node << 1] ^= 1;
lz[(node << 1) | 1] ^= 1;
} lz[node] = 0;
}
if (r < s || e < l || e < s)
return 0;
else if (l <= s && e <= r)
return t[node];
int p, q, m = s + (e - s) / 2;
p = query(node << 1, s, m, l, r);
q = query((node << 1) | 1, m + 1, e, l, r);
return p + q;
}
int main() {
int n, q, t, a, b;
scanf("%d%d", &n, &q);
while (q--) {
scanf("%d%d%d", &t, &a, &b);
a++;
b++;
if (t) {
printf("%d\n", query(1, 1, n, a, b));
}
else {
update(1, 1, n, a, b);
}
}
return 0;
}
Solution in C++ :
#include<bits/stdc++.h>
typedef long long ll;
using namespace std;
ll seg[400010];
ll lazy[400010];
void up(int in,int l,int r,int sl,int sr)
{
if(lazy[in]!=0)
{
seg[in]=(sr-sl+1)-seg[in];
if(sl!=sr){
lazy[2*in]=!lazy[2*in];
lazy[2*in+1]=!lazy[2*in+1];
}
lazy[in]=0;
}
if(r<sl || l>sr || l>r)return;
if(sl>=l && sr<=r)
{
seg[in]=(sr-sl+1)-seg[in];
if(sl!=sr){
lazy[2*in]=!lazy[2*in];
lazy[2*in+1]=!lazy[2*in+1];
}
return;
}
int mid=sl+(sr-sl)/2;
up(in*2,l,r,sl,mid);
up(in*2+1,l,r,mid+1,sr);
seg[in]=seg[in*2]+seg[in*2+1];
}
ll sum(int in,int l,int r,int sl,int sr)
{
if(lazy[in]!=0)
{
seg[in]=(sr-sl+1)-seg[in];
if(sl!=sr){
lazy[2*in]=!lazy[2*in];
lazy[2*in+1]=!lazy[2*in+1];
}
lazy[in]=0;
}
if(r<sl || l>sr || l>r)return 0;
if(sl>=l && sr<=r)
return seg[in];
int mid=sl+(sr-sl)/2;
return sum(in*2,l,r,sl,mid) + sum(in*2+1,l,r,mid+1,sr);
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int n,q;
cin>>n>>q;
while(q--)
{
int x,l,r;
cin>>x>>l>>r;
if(x==0)
up(1,l,r,0,n-1);
else{
cout<<sum(1,l,r,0,n-1)<<"\n";
}
}
}
Solution in Java :
/* package codechef; // don't place package name! */
import java.util.*;
import java.lang.*;
import java.io.*;
/* Name of the class has to be "Main" only if the class is public. */
class Codechef
{
public static void main (String[] args) throws java.lang.Exception
{
// your code goes here
InputStream inputStream=System.in;
InputReader sc = new InputReader(inputStream);
PrintWriter out=new PrintWriter(System.out);
int n=sc.nextInt();
int q=sc.nextInt();
BitSet bs=new BitSet(n);
StringBuffer sb=new StringBuffer();
for(int i=0;i<q;i++)
{
int x=sc.nextInt();
int a=sc.nextInt();
int b=sc.nextInt();
if(x==1)
{
sb.append(bs.get(a,b+1).cardinality()+"\n");
}
else
{
bs.flip(a,b+1);
}
}
System.out.println(sb.toString());
out.flush();
}
static class InputReader {
public BufferedReader reader;
public StringTokenizer tokenizer;
public InputReader(InputStream stream) {
reader = new BufferedReader(new InputStreamReader(stream), 32768);
tokenizer = null;
}
public String next() {
while (tokenizer == null || !tokenizer.hasMoreTokens()) {
try {
tokenizer = new StringTokenizer(reader.readLine());
} catch (IOException e) {
throw new RuntimeException(e);
}
}
return tokenizer.nextToken();
}
public int nextInt() {
return Integer.parseInt(next());
}
}
}
Solution in Python :
import numpy as np
n,q=map(int,input().split())
dp=np.zeros(n,dtype=bool)
while q>0:
zero,a,b=map(int,input().split())
if zero:print(np.count_nonzero(dp[a:b+1]))
else:dp[a:b+1]=~dp[a:b+1]
q-=1
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