feat: implemented page replacement algorithms

Src/PageReplacementAlgorithm/main.cpp

@@ -0,0 +1,184 @@
+#include <iostream>
+#include <vector>
+#include <iomanip>
+using namespace std;
+void printFrames(const vector<int>& frames) {
+    cout << "Frames: ";
+    for (int f : frames) {
+        if (f == -1) cout << "- ";
+        else cout << f << " ";
+    }
+    cout << endl;
+}
+void simulateFIFO(int framesCount, const vector<int>& pages) {
+    vector<int> frames(framesCount, -1);
+    int pointer = 0, hits = 0, misses = 0;
+
+    cout << "\n===== FIFO Page Replacement =====\n";
+
+    for (int p : pages) {
+        bool hit = false;
+        for (int f : frames) {
+            if (f == p) { hit = true; break; }
+        }
+
+        if (hit) {
+            hits++;
+            cout << "Page " << p << ": HIT  | ";
+        } else {
+            misses++;
+            frames[pointer] = p;
+            pointer = (pointer + 1) % framesCount;
+            cout << "Page " << p << ": MISS | ";
+        }
+
+        printFrames(frames);
+    }
+
+    cout << "\nTotal Hits  : " << hits;
+    cout << "\nTotal Misses: " << misses;
+    cout << "\nHit Ratio   : " << fixed << setprecision(2) 
+         << (double)hits / pages.size() << endl;
+}
+void simulateLRU(int framesCount, const vector<int>& pages) {
+    vector<int> frames(framesCount, -1);
+    vector<int> lastUsed(framesCount, -1);
+    int time = 0, hits = 0, misses = 0;
+
+    cout << "\n===== LRU Page Replacement =====\n";
+
+    for (int p : pages) {
+        time++;
+        bool hit = false;
+        for (int i = 0; i < framesCount; i++) {
+            if (frames[i] == p) {
+                hit = true;
+                lastUsed[i] = time;
+                break;
+            }
+        }
+
+        if (hit) {
+            hits++;
+            cout << "Page " << p << ": HIT  | ";
+        } else {
+            misses++;
+
+            int replaceIndex = -1;
+            for (int i = 0; i < framesCount; i++) {
+                if (frames[i] == -1) {
+                    replaceIndex = i;
+                    break;
+                }
+            }
+            if (replaceIndex == -1) {
+                int minTime = lastUsed[0];
+                replaceIndex = 0;
+
+                for (int i = 1; i < framesCount; i++) {
+                    if (lastUsed[i] < minTime) {
+                        minTime = lastUsed[i];
+                        replaceIndex = i;
+                    }
+                }
+            }
+
+            frames[replaceIndex] = p;
+            lastUsed[replaceIndex] = time;
+            cout << "Page " << p << ": MISS | ";
+        }
+
+        printFrames(frames);
+    }
+
+    cout << "\nTotal Hits  : " << hits;
+    cout << "\nTotal Misses: " << misses;
+    cout << "\nHit Ratio   : " << fixed << setprecision(2) 
+         << (double)hits / pages.size() << endl;
+}
+void simulateOptimal(int framesCount, const vector<int>& pages) {
+    vector<int> frames(framesCount, -1);
+    int hits = 0, misses = 0;
+
+    cout << "\n===== Optimal Page Replacement =====\n";
+
+    for (int i = 0; i < (int)pages.size(); i++) {
+        int p = pages[i];
+        bool hit = false;
+        for (int f : frames) {
+            if (f == p) { hit = true; break; }
+        }
+
+        if (hit) {
+            hits++;
+            cout << "Page " << p << ": HIT  | ";
+        } else {
+            misses++;
+            int replaceIdx = -1;
+            for (int j = 0; j < framesCount; j++) {
+                if (frames[j] == -1) {
+                    replaceIdx = j;
+                    break;
+                }
+            }
+            if (replaceIdx == -1) {
+                int farthest = -1;
+                for (int j = 0; j < framesCount; j++) {
+                    int nextUse = -1;
+                    for (int k = i + 1; k < (int)pages.size(); k++) {
+                        if (pages[k] == frames[j]) {
+                            nextUse = k;
+                            break;
+                        }
+                    }
+                    if (nextUse == -1) {
+                        replaceIdx = j;
+                        break;
+                    }
+
+                    if (nextUse > farthest) {
+                        farthest = nextUse;
+                        replaceIdx = j;
+                    }
+                }
+            }
+
+            frames[replaceIdx] = p;
+            cout << "Page " << p << ": MISS | ";
+        }
+
+        printFrames(frames);
+    }
+
+    cout << "\nTotal Hits  : " << hits;
+    cout << "\nTotal Misses: " << misses;
+    cout << "\nHit Ratio   : " << fixed << setprecision(2) 
+         << (double)hits / pages.size() << endl;
+}
+
+int main() {
+    int framesCount, n, choice;
+    cout << "Enter number of frames: ";
+    cin >> framesCount;
+
+    cout << "Enter number of page requests: ";
+    cin >> n;
+
+    vector<int> pages(n);
+    cout << "Enter the page reference string:\n";
+    for (int i = 0; i < n; i++) cin >> pages[i];
+
+    cout << "\nChoose Algorithm:\n";
+    cout << "1. FIFO\n2. LRU\n3. Optimal\n";
+    cout << "Enter choice: ";
+    cin >> choice;
+
+    switch (choice) {
+        case 1: simulateFIFO(framesCount, pages); break;
+        case 2: simulateLRU(framesCount, pages); break;
+        case 3: simulateOptimal(framesCount, pages); break;
+        default: cout << "Invalid choice!\n";
+    }
+
+    return 0;
+}