for ex-↵
Write a cpp program to check whether 1 to 10 integer values exits in array or not↵
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// for default values to map↵
_struct node {_↵
_ int value = -1;_↵
_};_↵
__ ↵
_// driver function_↵
__ ↵
_int main()_↵
_{_↵
_ // Empty map container_↵
__ ↵
_ map<int, node> mp;_↵
__ ↵
_ int a[10] = { 1, 3, 4, 10, 7, 6, 5, 2, 11 };_↵
_ // Inserting elements in map_↵
_ // assigning 1 to values of array...by default they are -1_↵
__ ↵
_ for (int i = 0; i < 10; i++)_↵
_ mp[a[i]].value = 1;_↵
__ ↵
_ for (int i = 1; i <= 10; i++) {_↵
_ if (mp[i].value == -1)_↵
_ cout << i << " does not exist\n";_↵
_ }_↵
_}_↵
Input : 1 3 4 10 7 6 5 2 11 ↵
Output :8 does not exist↵
9 does not exist↵
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// for default values to map↵
struct node {↵
int value = -1;↵
};↵
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// driver function↵
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int main()↵
{↵
// Empty map container↵
map<int, int> mp1;↵
cout << mp1[0] << "\n";↵
map<int, node> mp2;↵
cout << mp2[0].value;↵
}↵
Run on IDE↵
Output:↵
0↵
-1↵
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So how does this work??↵
Primitive datatypes(Int, Char, Bool, Float etc) in CPP are undefined if not initialised, but in case of struct or Map they are initialised with some default values. So in above example we have created a user defined datatype struct with name node and assigned default value -1 to it.↵
NOTE: By default map have default values but by using above method we can change it according to our need↵
int — 0↵
float — 0↵
bool — 0↵
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