adding caesar cipher

caesar-cipher/Cargo.toml

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+[package]
+name = "caesar-cipher"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

caesar-cipher/Makefile

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+format:
+	cargo fmt --quiet
+
+lint:
+	cargo clippy --quiet
+
+test:
+	cargo test --quiet
+
+run:
+	cargo run 
+
+all: format lint test run

caesar-cipher/src/lib.rs

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+/*
+This code defines two functions: encrypt and decrypt.
+The encrypt function takes a plaintext string and a shift value, and returns the ciphertext string. The decrypt function takes a ciphertext string and a shift value,
+and returns the plaintext string.
+
+*/
+
+pub fn encrypt(text: &str, shift: u8) -> String {
+    let mut result = String::new();
+    for c in text.chars() {
+        if c.is_ascii_alphabetic() {
+            let base = if c.is_ascii_lowercase() { b'a' } else { b'A' };
+            let offset = (c as u8 - base + shift) % 26;
+            result.push((base + offset) as char);
+        } else {
+            result.push(c);
+        }
+    }
+    result
+}
+
+pub fn decrypt(text: &str, shift: u8) -> String {
+    encrypt(text, 26 - shift)
+}

caesar-cipher/src/main.rs

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+/*
+This code defines two functions: encrypt and decrypt.
+The encrypt function takes a plaintext string and a shift value,
+and returns the ciphertext string.
+The decrypt function takes a ciphertext string and a shift value,
+and returns the plaintext string.
+
+*/
+
+use caesar_cipher::decrypt;
+use caesar_cipher::encrypt;
+
+fn main() {
+    let plaintext = "the quick brown fox jumps over the lazy dog";
+    let shift = 3;
+    let ciphertext = encrypt(plaintext, shift);
+    let decrypted_text = decrypt(&ciphertext, shift);
+    println!("Plaintext: {}", plaintext);
+    println!("Ciphertext: {}", ciphertext);
+    println!("Decrypted text: {}", decrypted_text);
+}