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Data Structures and Algorithms → Introduction to DSA 40

A God class (class that does everything) violates:
Single Responsibility Principle
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What is composition over inheritance principle?
Prefer building objects from components rather than inheriting
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Law of Demeter (Principle of Least Knowledge) says:
Object should only talk to immediate friends (not friends of friends)
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Which is an anti-pattern?
Singleton overuse, God class, Copy-paste programming
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The output of: class C{int x; public: C():x(0){} C(int x):x(x){} void print(){cout<<x;} }; C c1,c2(5); c1.print(); c2.print();
05
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The output of: class A{public:int x; A(int x):x(x){}}; A a(5); cout<<a.x;
5
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The output of: int f(int n){return n<=1 ? 1 : n*f(n-1);} cout<<f(5);
120
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The output of: int f(int n){return n<=1 ? n : f(n-1)+f(n-2);} cout<<f(7);
13
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The output of: int gcd(int a,int b){return b==0?a:gcd(b,a%b);} cout<<gcd(18);
6
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The output of: int power(int b,int e){return e==0?1:b*power(b,e-1);} cout<<power(8);
256
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Fast power (exponentiation by squaring) computes a^n in:
O(log n)
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The output of: int arr[]={5,3,8,1,9,2}; sort(arr,arr+6); cout<<arr[0]<<" "<<arr[5];
1 9
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The output of: int arr[]={1,2,3,4,5}; cout<<*max_element(arr,arr+5)<<" "<<*min_element(arr,arr+5);
5 1
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The output of: string s="Hello World"; transform(s.begin(),s.end(),s.begin(),toupper); cout<<s;
HELLO WORLD
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The output of: vector<int> v={1,2,3}; v.resize(5); cout<<v[4];
0
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The output of: string s="abcabc"; cout<<count(s.begin(),s.end(),a);
2
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The output of: cout<<boolalpha<<(3>2)<<" "<<(2>3);
true false
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What is the output: int x=42; cout<<hex<<x<<" "<<dec<<x;
2a 42
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The output of: int a[]={1,2,3,4,5}; cout<<sizeof(a)/sizeof(*a);
5
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The output of: vector<int> v={3,1,4,1,5,9}; sort(v.begin(),v.end()); v.erase(unique(v.begin(),v.end()),v.end()); cout<<v.size();
5
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What is the output: map<int,int> m={{1,10},{2,20},{3,30}}; for(auto [k,v]:m) cout<<k<<v;
102030
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The output of: auto v=vector<int>(5); iota(v.begin(),v.end(),1); cout<<v[3];
4
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The output of: int n=10; int sum=accumulate(begin({1,2,3,4,5,6,7,8,9,10}),end({1,2,3,4,5,6,7,8,9,10}),0); cout<<sum;
55
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The output of: string s="Race Car"; remove_if(s.begin(),s.end(),::isspace); cout<<s;
Race Car
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The output of: auto s=set<int>{5,3,1,4,2}; cout<<distance(s.begin(),s.end());
5
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The output of: int x=7; cout<<(x%2==0?"Even":"Odd")<<" "<<(x>0?"Pos":"NonPos");
Odd Pos
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What is the output: int x=0; do {x++; if(x==3) break;} while(x<10); cout<<x;
3
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The output of: int a=2; switch(a){case 1: case 2: cout<<"1or2"; break; case 3: cout<<"3";}
1or2
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The output of: int x=5; if(x>0) if(x>3) cout<<"A"; else cout<<"B"; else cout<<"C";
A
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The output of: int x=1; if(x>0) if(x>3) cout<<"A"; else cout<<"B"; else cout<<"C";
B
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The output of: int x=-1; if(x>0) if(x>3) cout<<"A"; else cout<<"B"; else cout<<"C";
C
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The output of: int i=0; for(;;){if(i++>=3) break; cout<<i;} cout<<i;
1235
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What is the output: int n=1234; int rev=0; while(n){rev=rev*10+n%10; n/=10;} cout<<rev;
4321
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The output of: int n=121; bool isPalin=true; int tmp=n,rev=0; while(tmp){rev=rev*10+tmp%10;tmp/=10;} cout<<(rev==n?"Yes":"No");
Yes
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The output of: int n=123; int sum=0; while(n){sum+=n%10; n/=10;} cout<<sum;
6
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The output of: int n=153; int sum=0,tmp=n; while(tmp){int d=tmp%10; sum+=d*d*d; tmp/=10;} cout<<(sum==n?"Armstrong":"Not");
Armstrong
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The output of: int n=6; int sum=0; for(int i=1;i<n;i++) if(n%i==0) sum+=i; cout<<(sum==n?"Perfect":"Not");
Perfect
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What is the output: int x=10; void* p=&x; cout<<*(int*)p;
10
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The output of: int arr[]={1,2,3,4,5}; int *p=arr; cout<<p[2];
3
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The output of: int x=5; int &r=x; int &s=r; s=10; cout<<x;
10
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