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Signed-off-by: Fabiana 🚀 Campanari <113218619+FabianaCampanari@users.noreply.github.com>
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README.md

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@@ -1146,9 +1146,118 @@ The transportation problem is a special type of **Linear Programming** that can
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These specialized algorithms are **faster** and **simpler** due to the regular structure of the transportation tableau.
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<br>
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#
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## 📈 Transportation Algorithm & Simplex Connection:
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The transportation algorithm follows the **same logic as the Simplex method**, but with **simplifications** tailored to the structure of transportation problems:
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### 🔹 1st Phase: Initial Basic Feasible Solution
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We will use two methods to find a basic solution:
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- **Northwest Corner Method**
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- **Least Cost Method**
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These provide starting points for optimization.
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<br>
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### 🔹 2nd Phase: Optimality Check:
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After obtaining a feasible solution, we check for optimality using methods like:
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- **MODI Method** (Modified Distribution)
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- **Stepping Stone Method**
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These determine whether cost can be further reduced by adjusting flows along loops in the matrix.
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<br>
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#
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## 🧭 Northwest Corner Method (Método do Canto Noroeste)
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This is a method to generate an initial feasible solution without considering transportation costs.
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<br>
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### 🔹 Steps:
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1. **Start in the top-left (northwest) corner** of the transportation table.
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- This is always cell $begin:math:text$ x_{11} $end:math:text$.
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2. **Allocate as much as possible** to the selected cell, respecting the available supply and demand.
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3. **Block the row or column** where the supply or demand has been fully used (but only one if both are zero simultaneously).
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- Mark the blocked row/column with an 'x'.
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- This ensures that some basic variables have zero values (necessary for basic feasible solution).
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4. **Repeat** the steps with the next unblocked cell in the top-left of the remaining matrix.
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🔁 Continue until all cells are either allocated or blocked.
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🟢 This method is **simple and quick**, but not necessarily optimal — further optimization is done in the next phase.
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<br>
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#
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## 💸 Least Cost Method (Método do Custo Mínimo)
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This method takes into account the transportation costs to guide the initial allocation.
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<br>
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### 🔹 Steps:
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1. **Identify the cell with the lowest unit cost** in the cost matrix among the remaining unallocated cells.
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2. **Allocate as much as possible** to this cell, without exceeding supply or demand constraints.
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3. **Adjust the supply and demand** for the row and column of the allocated cell.
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4. **Remove** (cross out) the row or column where supply or demand becomes zero. If both are zero simultaneously, cross out only one to maintain feasibility.
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5. **Repeat** the steps until all supplies and demands are met.
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⚠️ Unlike the Northwest Corner, this method **considers the costs** and usually leads to a **better initial solution**, closer to the optimal.
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<br>
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#
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## 🔍 Link to Risk Analysis
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- Unbalanced models simulate **shortage/surplus risks**.
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- Dummy rows/columns help visualize **operational failures**.
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- Solutions help identify:
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- Where **stockouts** will occur
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- How to **redistribute resources**
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- Costs of **unserved demands**
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This makes the model highly applicable to **supply chain risk management, disaster response logistics, and critical infrastructure planning**.
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<br>
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#
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## 📐 Initial Basic Feasible Solution
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A basic feasible solution must:
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1. Satisfy **all row (supply)** and **column (demand)** constraints.
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2. Include exactly **(m + n − 1)** basic variables (with m origins and n destinations).
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3. Avoid **closed loops (cycles)** in the tableau — these are patterns where allocation forms a polygon that violates independence.
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These principles ensure a **non-degenerate** starting point for iterative improvement algorithms like MODI.
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#
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## 🧩 Summary
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The transportation problem provides a clear, visual way to:
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- Model **linear resource flows**,
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- Simulate **imbalances and failure points**,
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- Optimize with **tailored algorithms**, and
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- Integrate with **Simplex** and **risk frameworks** for smarter planning.
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It's a cornerstone of **Operational Research**, **Logistics**, and **Decision Science**.
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