Fix: out-of-bounds issue in counting_sort_string.cpp (#3055)

Author: The-AarushiSingh

sorting/counting_sort_string.cpp

@@ -3,23 +3,21 @@
 
 using namespace std;
 
-void countSort(string arr) {
-    string output;
+void countSort(string& arr) {
+    int n = arr.length();
+    string output(n, ' ');  // pre-allocate space
 
-    int count[256], i;
-    for (int i = 0; i < 256; i++) count[i] = 0;
+    int count[256] = {0};
+    for (int i = 0; i < n; ++i) ++count[(unsigned char)arr[i]];
 
-    for (i = 0; arr[i]; ++i) ++count[arr[i]];
+    for (int i = 1; i < 256; ++i) count[i] += count[i - 1];
 
-    for (i = 1; i < 256; ++i) count[i] += count[i - 1];
-
-    for (i = 0; arr[i]; ++i) {
-        output[count[arr[i]] - 1] = arr[i];
-        --count[arr[i]];
+    for (int i = 0; i < n; ++i) {
+        output[count[(unsigned char)arr[i]] - 1] = arr[i];
+        --count[(unsigned char)arr[i]];
     }
 
-    for (i = 0; arr[i]; ++i) arr[i] = output[i];
-
+    arr = output;
     cout << "Sorted character array is " << arr;
 }