feat: mergesort algorithm

1 files changed, 53 insertions, 0 deletions

diff --git a/I_anno/Programmazione_2/mergesort.cc b/I_anno/Programmazione_2/mergesort.cc
new file mode 100644
index 0000000..6df83e5
--- /dev/null
+++ b/I_anno/Programmazione_2/mergesort.cc
@@ -0,0 +1,53 @@
+#include<iostream>
+
+using namespace std;
+
+void merge(int A[], int l, int q, int r) {
+    int size = (sizeof(*A)*2)+1;
+    int i = l;
+    int j = q+1;
+    int k = l;
+    int B[size];
+
+    while((i <= q) && (j <= r)) {
+        if(A[i] <= A[j])
+            B[k] = A[i++];
+        else
+            B[k] = A[j++];
+
+        k++;
+    }
+
+    while(i <= q)
+        B[k++] = A[i++];
+
+    while(j <= r)
+        B[k++] = A[j++];
+
+    for(k = l; k <= r; ++k) 
+        A[k] = B[k];
+}
+
+void mergesort(int A[], int l, int r) {
+    if(l < r) {
+        int q = (l+r)/2;
+        mergesort(A, l, q);
+        mergesort(A, q+1, r);
+        merge(A, l, q, r);
+    }
+}
+
+
+int main() {
+    int a[] = {2, 4, 72, 100, 2, 12, 0, 0, 1, 23, 45, 12, 120, 3, 6};
+    for(int i = 0; i < 15; ++i) {
+        cout << a[i] << ' ';
+    }
+    cout << endl;
+    mergesort(a, 0, 14);
+    for(int i = 0; i < 15; ++i) {
+        cout << a[i] << ' ';
+    }
+
+    return 0;
+}