Add `countingsort`

1 files changed, 83 insertions, 0 deletions

diff --git a/Year_2/Algorithms/data_structures/cc/countingsort.cc b/Year_2/Algorithms/data_structures/cc/countingsort.cc
new file mode 100644
index 0000000..49f29d7
--- /dev/null
+++ b/Year_2/Algorithms/data_structures/cc/countingsort.cc
@@ -0,0 +1,83 @@
+#include <fstream>
+#include <iostream>
+#include <string.h>
+#include <string>
+
+using namespace std;
+
+void
+counting_sort(int* A, size_t n, ofstream& fout)
+{
+    int i, j;
+    int max, min;
+    int* freq;
+    int* t;
+    int range;
+
+    max = A[0], min = A[0];
+    t = new int[n];
+
+    for (i = 1; i < n; ++i) {
+        if (A[i] > max)
+            max = A[i];
+
+        if (A[i] < min)
+            min = A[i];
+    }
+
+    range = (max - min) + 1;
+
+    freq = new int[range];
+
+    for (i = 0; i < range; ++i) {
+        freq[i] = 0;
+    }
+
+    for (i = 0; i < n; ++i) {
+        freq[A[i] - min] += 1;
+    }
+    for (i = 1; i < range; ++i) {
+        freq[i] = freq[i] + freq[i - 1];
+    }
+    fout << "0 ";
+    for (i = 0; i < range - 1; ++i) {
+        fout << freq[i] << ' ';
+    }
+
+    for (i = n - 1; i >= 0; --i) {
+        t[freq[A[i] - min] - 1] = A[i];
+        freq[A[i] - min]--;
+    }
+
+    for (i = 0; i < n; ++i) {
+        A[i] = t[i];
+        fout << A[i] << ' ';
+    }
+    fout << endl;
+
+    delete[] freq;
+    delete[] t;
+}
+
+int
+main()
+{
+    ifstream fin("input.txt");
+    ofstream fout("output.txt");
+    int N;
+
+    for (int i = 0; i < 100; ++i) {
+        fin >> N;
+        int* a = new int[N];
+
+        for (int j = 0; j < N; ++j) {
+            fin >> a[j];
+        }
+
+        counting_sort(a, N, fout);
+
+        delete[] a;
+    }
+
+    return 0;
+}