From 9019283341ab77e9a50d2a6f2d04680224efab4a Mon Sep 17 00:00:00 2001
From: omi <sowmithbasak13@gmail.com>
Date: Sun, 26 Oct 2025 23:46:40 +0530
Subject: [PATCH 1/9] added npv, compound interest and payback period

---
 src/financial/compound_interest.rs | 24 ++++++++++++++++
 src/financial/mod.rs               |  6 ++++
 src/financial/npv.rs               | 44 ++++++++++++++++++++++++++++++
 src/financial/payback.rs           | 30 ++++++++++++++++++++
 4 files changed, 104 insertions(+)
 create mode 100644 src/financial/compound_interest.rs
 create mode 100644 src/financial/npv.rs
 create mode 100644 src/financial/payback.rs

diff --git a/src/financial/compound_interest.rs b/src/financial/compound_interest.rs
new file mode 100644
index 00000000000..d348078ddcc
--- /dev/null
+++ b/src/financial/compound_interest.rs
@@ -0,0 +1,24 @@
+// compound interest is given by A = P(1+r/n)^nt
+// where: A = Final Amount, P = Principal Amount, r = rate of interest,
+// n = number of times interest is compounded per year and t = time (in years)
+
+pub fn compound_interest(princpal: f64, rate: f64, comp_per_year: u32, years: f64) -> f64 {
+    let amount = princpal * (1.00 + rate / comp_per_year as f64).powf(comp_per_year as f64 * years);
+    return amount;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_compound_interest() {
+        let principal = 1000.0;
+        let rate = 0.05; // 5% annual interest
+        let times_per_year = 4; // interest compounded quarterly
+        let years = 2.0; // 2 years tenure
+        let result = compound_interest(principal, rate, times_per_year, years);
+        assert!((result - 1104.486).abs() < 0.001); // expected value rounded up to 3 decimal
+                                                    // places
+    }
+}
diff --git a/src/financial/mod.rs b/src/financial/mod.rs
index 89b36bfa5e0..b257aec4d7a 100644
--- a/src/financial/mod.rs
+++ b/src/financial/mod.rs
@@ -1,2 +1,8 @@
+mod compound_interest;
+mod npv;
+mod payback;
 mod present_value;
+pub use compound_interest::compound_interest;
+pub use npv::npv;
+pub use payback;
 pub use present_value::present_value;
diff --git a/src/financial/npv.rs b/src/financial/npv.rs
new file mode 100644
index 00000000000..d194fa302ff
--- /dev/null
+++ b/src/financial/npv.rs
@@ -0,0 +1,44 @@
+/// Calculates Net Present Value given a vector of cash flows and a discount rate.
+/// cash_flows: Vector of f64 representing cash flows for each period.
+/// rate: Discount rate as an f64 (e.g., 0.05 for 5%)
+
+pub fn npv(cash_flows: &[f64], rate: f64) -> f64 {
+    cash_flows
+        .iter()
+        .enumerate()
+        .map(|(t, &cf)| cf / (1.00 + rate).powi(t as i32))
+        .sum()
+}
+
+// tests
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_npv_basic() {
+        let cash_flows = vec![-1000.0, 300.0, 400.0, -50.0];
+        let rate = 0.10;
+        let result = npv(&cash_flows, rate);
+        // Calculated value ≈ -434.25
+        assert!((result - (-434.25)).abs() < 0.05); // Allow small margin of error
+    }
+
+    #[test]
+    fn test_npv_zero_rate() {
+        let cash_flows = vec![100.0, 200.0, -50.0];
+        let rate = 0.0;
+        let result = npv(&cash_flows, rate);
+        assert!((result - 250.0).abs() < 0.05);
+    }
+
+    #[test]
+    fn test_npv_empty() {
+        // For empty cash flows: NPV should be 0
+        let cash_flows: Vec<f64> = vec![];
+        let rate = 0.05;
+        let result = npv(&cash_flows, rate);
+        assert_eq!(result, 0.0);
+    }
+}
diff --git a/src/financial/payback.rs b/src/financial/payback.rs
new file mode 100644
index 00000000000..012e50c503a
--- /dev/null
+++ b/src/financial/payback.rs
@@ -0,0 +1,30 @@
+/// Returns the payback period in years
+/// If investment is not paid back, returns None.
+
+pub fn payback(cash_flow: &[f64]) -> Option<usize> {
+    let mut total = 0.00;
+    for (year, &cf) in cash_flow.iter().enumerate() {
+        total += cf;
+        if total >= 0.00 {
+            return Some(year);
+        }
+    }
+    None
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_payback() {
+        let cash_flows = vec![-1000.0, 300.0, 400.0, 500.0];
+        assert_eq!(payback(&cash_flows), Some(3)); // paid back in year 3
+    }
+
+    #[test]
+    fn test_no_payback() {
+        let cash_flows = vec![-1000.0, 100.0, 100.0, 100.0];
+        assert_eq!(payback(&cash_flows), None); // never paid back
+    }
+}

From c202eeeb6975504b08d1f09091daa86bc33ac61b Mon Sep 17 00:00:00 2001
From: omi <sowmithbasak13@gmail.com>
Date: Sun, 26 Oct 2025 23:53:52 +0530
Subject: [PATCH 2/9] fixed mod.rs errors

---
 src/financial/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/financial/mod.rs b/src/financial/mod.rs
index b257aec4d7a..f1e11883fea 100644
--- a/src/financial/mod.rs
+++ b/src/financial/mod.rs
@@ -4,5 +4,5 @@ mod payback;
 mod present_value;
 pub use compound_interest::compound_interest;
 pub use npv::npv;
-pub use payback;
+pub use payback::payback;
 pub use present_value::present_value;

From 8f93f282553689e76b51cac146db93a06bcf5e4b Mon Sep 17 00:00:00 2001
From: omi <sowmithbasak13@gmail.com>
Date: Mon, 27 Oct 2025 00:00:03 +0530
Subject: [PATCH 3/9] added algos to DIRECTORY.md

---
 DIRECTORY.md | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/DIRECTORY.md b/DIRECTORY.md
index 7a800e41379..5edeaf0decc 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -105,6 +105,9 @@
     * [Word Break](https://github.com/TheAlgorithms/Rust/blob/master/src/dynamic_programming/word_break.rs)
   * Financial
     * [Present Value](https://github.com/TheAlgorithms/Rust/blob/master/src/financial/present_value.rs)
+    * [Net Present Value](https://github.com/TheAlgorithms/Rust/blob/master/src/financial/npv.rs)
+    * [Compound Interest](https://github.com/TheAlgorithms/Rust/blob/master/src/financial/compound_interest.rs)
+    * [Payback Period](https://github.com/TheAlgorithms/Rust/blob/master/src/financial/payback.rs)
   * General
     * [Convex Hull](https://github.com/TheAlgorithms/Rust/blob/master/src/general/convex_hull.rs)
     * [Fisher Yates Shuffle](https://github.com/TheAlgorithms/Rust/blob/master/src/general/fisher_yates_shuffle.rs)

From d29ce8c3af0fba8f65f2a174137500d3508da8fb Mon Sep 17 00:00:00 2001
From: omi <sowmithbasak13@gmail.com>
Date: Mon, 27 Oct 2025 07:26:55 +0530
Subject: [PATCH 4/9] fixed typos + removed 'return' keyword

---
 src/financial/compound_interest.rs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/financial/compound_interest.rs b/src/financial/compound_interest.rs
index d348078ddcc..664ea47805c 100644
--- a/src/financial/compound_interest.rs
+++ b/src/financial/compound_interest.rs
@@ -2,9 +2,10 @@
 // where: A = Final Amount, P = Principal Amount, r = rate of interest,
 // n = number of times interest is compounded per year and t = time (in years)
 
-pub fn compound_interest(princpal: f64, rate: f64, comp_per_year: u32, years: f64) -> f64 {
-    let amount = princpal * (1.00 + rate / comp_per_year as f64).powf(comp_per_year as f64 * years);
-    return amount;
+pub fn compound_interest(principal: f64, rate: f64, comp_per_year: u32, years: f64) -> f64 {
+    let amount =
+        principal * (1.00 + rate / comp_per_year as f64).powf(comp_per_year as f64 * years);
+    amount
 }
 
 #[cfg(test)]

From ec6f731a35979523b5bc8121e48d8bb6b021987f Mon Sep 17 00:00:00 2001
From: omi <sowmithbasak13@gmail.com>
Date: Mon, 27 Oct 2025 07:33:17 +0530
Subject: [PATCH 5/9] made the function more idiomatic to resolve clippy
 warnings

---
 src/financial/compound_interest.rs | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/financial/compound_interest.rs b/src/financial/compound_interest.rs
index 664ea47805c..e8fb7fffc33 100644
--- a/src/financial/compound_interest.rs
+++ b/src/financial/compound_interest.rs
@@ -3,9 +3,7 @@
 // n = number of times interest is compounded per year and t = time (in years)
 
 pub fn compound_interest(principal: f64, rate: f64, comp_per_year: u32, years: f64) -> f64 {
-    let amount =
-        principal * (1.00 + rate / comp_per_year as f64).powf(comp_per_year as f64 * years);
-    amount
+    principal * (1.00 + rate / comp_per_year as f64).powf(comp_per_year as f64 * years)
 }
 
 #[cfg(test)]

From 21541d8b16337b86cda2c1fa9f8e9444edf04ae6 Mon Sep 17 00:00:00 2001
From: Andrii Siriak <siryaka@gmail.com>
Date: Mon, 27 Oct 2025 09:28:23 +0200
Subject: [PATCH 6/9] Update src/financial/compound_interest.rs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 src/financial/compound_interest.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/financial/compound_interest.rs b/src/financial/compound_interest.rs
index e8fb7fffc33..bc3bfbc23e0 100644
--- a/src/financial/compound_interest.rs
+++ b/src/financial/compound_interest.rs
@@ -17,7 +17,7 @@ mod tests {
         let times_per_year = 4; // interest compounded quarterly
         let years = 2.0; // 2 years tenure
         let result = compound_interest(principal, rate, times_per_year, years);
-        assert!((result - 1104.486).abs() < 0.001); // expected value rounded up to 3 decimal
+        assert!((result - 1104.486).abs() < 0.001); // expected value rounded to 3 decimal
                                                     // places
     }
 }

From b629e90cfc5a1c9f45f6040527204003d181af2d Mon Sep 17 00:00:00 2001
From: omi <sowmithbasak13@gmail.com>
Date: Mon, 27 Oct 2025 20:23:05 +0530
Subject: [PATCH 7/9] added some finance ratios, NPV sensitivity and Treynor
 Ratio to financial module

---
 DIRECTORY.md                     |  3 ++
 src/financial/finance_ratios.rs  | 50 ++++++++++++++++++++++++++++++++
 src/financial/mod.rs             | 10 +++++++
 src/financial/npv_sensitivity.rs | 43 +++++++++++++++++++++++++++
 src/financial/treynor_ratio.rs   | 35 ++++++++++++++++++++++
 5 files changed, 141 insertions(+)
 create mode 100644 src/financial/finance_ratios.rs
 create mode 100644 src/financial/npv_sensitivity.rs
 create mode 100644 src/financial/treynor_ratio.rs

diff --git a/DIRECTORY.md b/DIRECTORY.md
index 20d835b41e2..c6ce922d13f 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -106,8 +106,11 @@
   * Financial
     * [Present Value](https://github.com/TheAlgorithms/Rust/blob/master/src/financial/present_value.rs)
     * [Net Present Value](https://github.com/TheAlgorithms/Rust/blob/master/src/financial/npv.rs)
+    * [NPV Sensitivity](https://github.com/TheAlgorithms/Rust/blob/master/src/financial/npv_sensitivity.rs)
     * [Compound Interest](https://github.com/TheAlgorithms/Rust/blob/master/src/financial/compound_interest.rs)
     * [Payback Period](https://github.com/TheAlgorithms/Rust/blob/master/src/financial/payback.rs)
+    * [Finance Ratios](https://github.com/TheAlgorithms/Rust/blob/master/src/financial/finance_ratios.rs)
+    * [Treynor Ratio](https://github.com/TheAlgorithms/Rust/blob/master/src/financial/treynor_ratio.rs)
   * General
     * [Convex Hull](https://github.com/TheAlgorithms/Rust/blob/master/src/general/convex_hull.rs)
     * [Fisher Yates Shuffle](https://github.com/TheAlgorithms/Rust/blob/master/src/general/fisher_yates_shuffle.rs)
diff --git a/src/financial/finance_ratios.rs b/src/financial/finance_ratios.rs
new file mode 100644
index 00000000000..035d3cacf8a
--- /dev/null
+++ b/src/financial/finance_ratios.rs
@@ -0,0 +1,50 @@
+// Calculating simple ratios like Return on Investment (ROI), Debt to Equity, Gross Profit Margin
+// and Earnings per Sale (EPS)
+pub fn return_on_investment(gain: f64, cost: f64) -> f64 {
+    (gain - cost) / cost
+}
+
+pub fn debt_to_equity(debt: f64, equity: f64) -> f64 {
+    debt / equity
+}
+
+pub fn gross_profit_margin(revenue: f64, cost: f64) -> f64 {
+    (revenue - cost) / revenue
+}
+
+pub fn earnings_per_sale(net_income: f64, pref_dividend: f64, share_avg: f64) -> f64 {
+    (net_income - pref_dividend) / share_avg
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_return_on_investment() {
+        // let gain = 1200, cost = 1000 thus, ROI = (1200 - 1000)/1000 = 0.2
+        let result = return_on_investment(1200.0, 1000.0);
+        assert!((result - 0.2).abs() < 0.001);
+    }
+
+    #[test]
+    fn test_debt_to_equity() {
+        // let debt = 300, equity = 150 thus, debt to equity ratio = 300/150 = 2
+        let result = debt_to_equity(300.0, 150.0);
+        assert!((result - 2.0).abs() < 0.001);
+    }
+
+    #[test]
+    fn test_gross_profit_margin() {
+        // let revenue = 1000, cost = 800 thus, gross profit margin = (1000-800)/1000 = 0.2
+        let result = gross_profit_margin(1000.0, 800.0);
+        assert!((result - 0.2).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_earnings_per_sale() {
+        // let net_income = 350, pref_dividend = 50, share_avg = 25 this EPS = (350-50)/25 = 12
+        let result = earnings_per_sale(350.0, 50.0, 25.0);
+        assert!((result - 12.0).abs() < 0.001);
+    }
+}
diff --git a/src/financial/mod.rs b/src/financial/mod.rs
index f1e11883fea..66fb54a3f57 100644
--- a/src/financial/mod.rs
+++ b/src/financial/mod.rs
@@ -1,8 +1,18 @@
 mod compound_interest;
+mod finance_ratios;
 mod npv;
+mod npv_sensitivity;
 mod payback;
 mod present_value;
+mod treynor_ratio;
 pub use compound_interest::compound_interest;
 pub use npv::npv;
+pub use npv_sensitivity::npv_sensitivity;
 pub use payback::payback;
 pub use present_value::present_value;
+pub use treynor_ratio::treynor_ratio;
+
+pub use finance_ratios::debt_to_equity;
+pub use finance_ratios::earnings_per_sale;
+pub use finance_ratios::gross_profit_margin;
+pub use finance_ratios::return_on_investment;
diff --git a/src/financial/npv_sensitivity.rs b/src/financial/npv_sensitivity.rs
new file mode 100644
index 00000000000..a65f552e89b
--- /dev/null
+++ b/src/financial/npv_sensitivity.rs
@@ -0,0 +1,43 @@
+/// Computes the Net Present Value (NPV) of a cash flow series
+/// at multiple discount rates to show sensitivity.
+///
+/// # Inputs:
+/// - `cash_flows`: A slice of cash flows, where each entry is a period value
+///   e.g., year 0 is initial investment, year 1+ are returns or costs
+/// - `discount_rates`: A slice of discount rates, e.g. `[0.05, 0.10, 0.20]`,
+///   where each rate is evaluated independently.
+///
+/// # Output:
+/// - Returns a vector of NPV values, each corresponding to a rate in `discount_rates`.
+///   For example, output is `[npv_rate1, npv_rate2, ...]`.
+
+pub fn npv_sensitivity(cash_flows: &[f64], discount_rates: &[f64]) -> Vec<f64> {
+    discount_rates
+        .iter()
+        .cloned()
+        .map(|rate| {
+            cash_flows
+                .iter()
+                .enumerate()
+                .map(|(t, &cf)| cf / (1.0 + rate).powi(t as i32))
+                .sum()
+        })
+        .collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_npv_sensitivity() {
+        let cashflows = vec![-1000.00, 400.00, 400.00, 400.00];
+        let rates = vec![0.05, 0.1, 0.2];
+        let expected = vec![89.30, -5.26, -157.41];
+        let out = npv_sensitivity(&cashflows, &rates);
+        assert_eq!(out.len(), 3);
+        // value check
+        for (o, e) in out.iter().zip(expected.iter()) {
+            assert!((o - e).abs() < 0.1);
+        }
+    }
+}
diff --git a/src/financial/treynor_ratio.rs b/src/financial/treynor_ratio.rs
new file mode 100644
index 00000000000..d53d7246f72
--- /dev/null
+++ b/src/financial/treynor_ratio.rs
@@ -0,0 +1,35 @@
+/// Calculates the Treynor Ratio for a portfolio.
+///
+/// # Inputs
+/// - `portfolio_return`: Portfolio return
+/// - `risk_free_rate`: Risk-free rate
+/// - `beta`: Portfolio beta
+/// where Beta is a financial metric that measures the systematic risk of a security or portfolio compared to the overall market.
+///
+/// # Output
+/// - Returns excess return per unit of market risk
+pub fn treynor_ratio(portfolio_return: f64, risk_free_rate: f64, beta: f64) -> f64 {
+    if beta == 0.0 {
+        f64::NAN
+    } else {
+        (portfolio_return - risk_free_rate) / beta
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_treynor_ratio() {
+        // for portfolio_return = 0.10, risk_free_rate = 0.05, beta = 1.5
+        // expected result: (0.10 - 0.05) / 1.5 = 0.033333...
+        assert!((treynor_ratio(0.10, 0.05, 1.50) - 0.03333).abs() < 0.01);
+    }
+
+    #[test]
+    fn test_treynor_ratio_empty_beta() {
+        // test for zero beta (undefined ratio)
+        assert!(treynor_ratio(0.10, 0.05, 0.00).is_nan());
+    }
+}

From 4875cb6ef81e9deefd67d345fb08ca637638a8ee Mon Sep 17 00:00:00 2001
From: omi <sowmithbasak13@gmail.com>
Date: Mon, 27 Oct 2025 20:30:23 +0530
Subject: [PATCH 8/9] fixed clippy warnings in npv_sensitivity.rs

---
 src/financial/npv_sensitivity.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/financial/npv_sensitivity.rs b/src/financial/npv_sensitivity.rs
index a65f552e89b..63b4d93fc8b 100644
--- a/src/financial/npv_sensitivity.rs
+++ b/src/financial/npv_sensitivity.rs
@@ -30,7 +30,7 @@ mod tests {
     use super::*;
     #[test]
     fn test_npv_sensitivity() {
-        let cashflows = vec![-1000.00, 400.00, 400.00, 400.00];
+        let cashflows = [-1000.00, 400.00, 400.00, 400.00];
         let rates = vec![0.05, 0.1, 0.2];
         let expected = vec![89.30, -5.26, -157.41];
         let out = npv_sensitivity(&cashflows, &rates);

From dbb9beedd22652b121de3d185637b970c61facce Mon Sep 17 00:00:00 2001
From: omi <sowmithbasak13@gmail.com>
Date: Mon, 27 Oct 2025 20:33:13 +0530
Subject: [PATCH 9/9] fixed clippy warnings in npv_sensitivity.rs

---
 src/financial/npv_sensitivity.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/financial/npv_sensitivity.rs b/src/financial/npv_sensitivity.rs
index 63b4d93fc8b..24853f29907 100644
--- a/src/financial/npv_sensitivity.rs
+++ b/src/financial/npv_sensitivity.rs
@@ -31,8 +31,8 @@ mod tests {
     #[test]
     fn test_npv_sensitivity() {
         let cashflows = [-1000.00, 400.00, 400.00, 400.00];
-        let rates = vec![0.05, 0.1, 0.2];
-        let expected = vec![89.30, -5.26, -157.41];
+        let rates = [0.05, 0.1, 0.2];
+        let expected = [89.30, -5.26, -157.41];
         let out = npv_sensitivity(&cashflows, &rates);
         assert_eq!(out.len(), 3);
         // value check