Merge pull request #351 from usmansafdarktk/main

Introduced genetic algorithms

Author: larymak

Data Structures and Algorithms/Genetic Algorithms/README.md

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+# Genetic Algorithms in Problem Solving
+
+## Overview
+This repository contains implementations of genetic algorithms (GAs) applied to solve various problems. Genetic algorithms are a family of optimization algorithms inspired by the process of natural selection. They are commonly used to find solutions for complex, non-linear, and multi-objective optimization problems. This collection demonstrates the application of GAs to address different problem domains.
+
+
+## Problem Domains
+- [Knapsack Problem](./knapsack/): Applying GAs to find the best combination of items within a weight limit.
+

Data Structures and Algorithms/Genetic Algorithms/knapsack_problem.py

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+import random
+import matplotlib.pyplot as plt
+
+"""
+This program uses a genetic algorithm to solve the 0/1 Knapsack problem. 
+In the Knapsack problem, you are given a set of items, each with a value and a weight, 
+and a knapsack with a weight limit. The goal is to select a combination of items 
+to maximize the total value without exceeding the weight limit. 
+This genetic algorithm iteratively evolves a population of candidate solutions to find the best combination.
+
+Knapsack Problem Parameters:
+- weight_limit: The weight limit of the knapsack.
+- item_list: A list of items, where each item is represented as (value, weight).
+
+Genetic Algorithm Parameters:
+- population_size: The size of the population.
+- max_generations: The maximum number of generations to run.
+- mutation_rate: The probability of mutation for each gene in the chromosome.
+- chromosome_length: The number of genes in each chromosome.
+"""
+
+# Knapsack Problem Parameters
+weight_limit = 56
+item_list = [(17, 1), (78, 20), (56, 34), (2, 15), (34, 21), (3, 10)]  # (value, weight)
+
+# Genetic Algorithm Parameters
+population_size = 100
+max_generations = 300
+mutation_rate = 0.5
+chromosome_length = len(item_list)
+
+
+def initialize_population():
+    # Initialize the population with random chromosomes
+    population = []
+    for _ in range(population_size):
+        chromosome = [random.randint(0, 1) for _ in range(chromosome_length)]
+        population.append(chromosome)
+    return population
+
+
+def calculate_fitness(chromosome):
+    # Calculate the fitness of a chromosome based on its value and weight
+    total_value = 0
+    total_weight = 0
+    for gene, item in zip(chromosome, item_list):
+        if gene == 1:
+            total_value += item[0]
+            total_weight += item[1]
+    if total_weight > weight_limit:
+        return 0  # Violates weight constraint
+    return total_value
+
+
+def selection(population):
+    # Select individuals from the population based on their fitness
+    selected = []
+    total_fitness = sum(calculate_fitness(chromosome) for chromosome in population)
+    for _ in range(population_size):
+        r = random.uniform(0, total_fitness)
+        cumulative_fitness = 0
+        for chromosome in population:
+            cumulative_fitness += calculate_fitness(chromosome)
+            if cumulative_fitness >= r:
+                selected.append(chromosome)
+                break
+    return selected
+
+
+def crossover(parent1, parent2):
+    # Perform one-point crossover to create two children
+    crossover_point = random.randint(1, chromosome_length - 1)
+    child1 = parent1[:crossover_point] + parent2[crossover_point:]
+    child2 = parent2[:crossover_point] + parent1[crossover_point:]
+    return child1, child2
+
+
+def mutation(chromosome):
+    # Apply mutation to a chromosome with a given probability
+    mutated_chromosome = chromosome[:]
+    for i in range(chromosome_length):
+        if random.random() < mutation_rate:
+            mutated_chromosome[i] = 1 - mutated_chromosome[i]
+    return mutated_chromosome
+
+
+def genetic_algorithm():
+    # Main genetic algorithm loop
+    population = initialize_population()
+    fitness_history = []
+    for generation in range(max_generations):
+        population = selection(population)
+        new_population = []
+        while len(new_population) < population_size:
+            parent1 = random.choice(population)
+            parent2 = random.choice(population)
+            child1, child2 = crossover(parent1, parent2)
+            mutated_child1 = mutation(child1)
+            mutated_child2 = mutation(child2)
+            new_population.extend([mutated_child1, mutated_child2])
+        
+        best_fit = max(calculate_fitness(chromosome) for chromosome in new_population)
+        fitness_history.append(best_fit)
+        
+        population = new_population
+
+    best_chromosome = max(population, key=calculate_fitness)
+    best_fitness = calculate_fitness(best_chromosome)
+
+    return best_chromosome, best_fitness, fitness_history
+
+
+# Run the genetic algorithm and print the result
+best_solution, best_fitness_value, fitness_history = genetic_algorithm()
+print("Best Solution:", best_solution)
+print("Best Fitness Value:", best_fitness_value)
+
+# Plot fitness history
+plt.plot(fitness_history)
+plt.title('Fitness History')
+plt.xlabel('Generation')
+plt.ylabel('Fitness')
+plt.show()