Generate Random Numbers in a Range
Suppose there are two numbers a and b, we want to generate a random number between them [a, b)
1. Generate Random Integer in a Range
Example:
C++
// C++ program to generate random integers#include <bits/stdc++.h>using namespace std;int randomInt(int a, int b){ if (a > b) return randomInt(b, a); if (a == b) return a; return a + (rand() % (b - a));}signed main(){ // seeds the generator srand(time(0)); // generate random integers in a range [ Min , Max ) for (int i = 0; i < 5; i++) { cout << randomInt(10, 20) << " "; } return 0;} |
Output
16 17 16 10 14
Time Complexity: O(1)
Auxiliary Space: O(1)
Now we can use this same concept to generate a random float number in a range
2. Generate Random Float Numbers in a Range
Example:
C++
// C++ program to generate random float numbers#include <bits/stdc++.h>using namespace std;float randomFloat(){ return (float)(rand()) / (float)(RAND_MAX);}int randomInt(int a, int b){ if (a > b) return randomInt(b, a); if (a == b) return a; return a + (rand() % (b - a));}float randomFloat(int a, int b){ if (a > b) return randomFloat(b, a); if (a == b) return a; return (float)randomInt(a, b) + randomFloat();}signed main(){ // seeds the generator srand(time(0)); // generate random float numbers in a // range [ Min , Max) for (int i = 0; i < 5; i++) { cout << randomFloat(10, 20) << "\n"; } return 0;} |
Output
10.859 19.3532 13.1625 18.3262 16.2245
Time Complexity: O(1)
Auxiliary Space: O(1)
Wrap Up:
Let us wrap up all the things in one example.
Example:
C++
// C++ program to generate random numbers#include <bits/stdc++.h>using namespace std;class Random {public: // constructor Random() { // seeds the generator srand(time(0)); } // generate random integer int randomInt() { return rand(); } // generate random integer in a range [Min , Max) int randomInt(int a, int b) { if (a > b) return randomInt(b, a); if (a == b) return a; return a + (rand() % (b - a)); } // generate random fraction float randomFloat() { return (float)(rand()) / (float)(RAND_MAX); } // generate random float in a range float randomFloat(int a, int b) { if (a > b) return randomFloat(b, a); if (a == b) return a; return (float)randomInt(a, b) + randomFloat(); }};signed main(){ Random random = Random(); // random integer cout << random.randomInt() << "\n"; // random integer in a range cout << random.randomInt(10, 15) << "\n"; // random float (fraction) cout << random.randomFloat() << "\n"; // random float in range cout << random.randomFloat(10, 15) << "\n"; return 0;} |
Output
1504136767 12 0.204022 13.5138
Time Complexity: O(1)
Auxiliary Space: O(1)
Generate a Random Float Number in C++
Random floating numbers can be generated using 2 methods:
- Using rand()
- Using uniform real distribution
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