Merge pull request #148 from NishantRana07/DSA3

Create Back-Tracking.README.md

Algorithmic Strategies/Back-Tracking.README.md

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+# <div align="Center">Backtracking Approach</div>
+
+### The backtracking approach in programming involves searching for a solution by trying various possibilities and backtracking when a solution cannot be achieved. It is used for problems that require exploring all possible configurations.
+<hr>
+
+### For Example :
+
+## Activity Selection Problem
+```
+#include <stdio.h>
+#include <stdbool.h>
+
+// Structure to represent an activity
+typedef struct {
+    int index;
+    int start;
+    int end;
+} Activity;
+
+void printSelectedActivities(bool selected[], Activity activities[], int n) {
+    printf("Selected activities are:\n");
+    for (int i = 0; i < n; i++) {
+        if (selected[i]) {
+            printf("Activity %d (Start: %d, End: %d)\n", activities[i].index, activities[i].start, activities[i].end);
+        }
+    }
+}
+
+bool isValidSelection(Activity activities[], bool selected[], int n, int current) {
+    for (int i = 0; i < current; i++) {
+        if (selected[i] && activities[current].start < activities[i].end) {
+            return false;
+        }
+    }
+    return true;
+}
+
+bool activitySelection(Activity activities[], bool selected[], int n, int current) {
+    if (current == n) {
+        printSelectedActivities(selected, activities, n);
+        return true;
+    }
+
+    selected[current] = true;
+    if (isValidSelection(activities, selected, n, current)) {
+        if (activitySelection(activities, selected, n, current + 1)) {
+            return true;
+        }
+    }
+
+    selected[current] = false;
+    return activitySelection(activities, selected, n, current + 1);
+}
+
+int main() {
+    Activity activities[] = {
+        {1, 1, 2},
+        {2, 3, 4},
+        {3, 0, 6},
+        {4, 5, 7},
+        {5, 8, 9},
+        {6, 5, 9}
+    };
+    int n = sizeof(activities) / sizeof(activities[0]);
+    bool selected[n];
+
+    for (int i = 0; i < n; i++) {
+        selected[i] = false;
+    }
+
+    activitySelection(activities, selected, n, 0);
+
+    return 0;
+}
+```