Add the initial EN translation for C++ code (#1346)

en/codes/cpp/chapter_searching/binary_search_edge.cpp

@@ -0,0 +1,66 @@
+/**
+ * File: binary_search_edge.cpp
+ * Created Time: 2023-08-04
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+
+/* Binary search for insertion point (with duplicate elements) */
+int binarySearchInsertion(const vector<int> &nums, int target) {
+    int i = 0, j = nums.size() - 1; // Initialize double closed interval [0, n-1]
+    while (i <= j) {
+        int m = i + (j - i) / 2; // Calculate midpoint index m
+        if (nums[m] < target) {
+            i = m + 1; // Target is in interval [m+1, j]
+        } else {
+            j = m - 1; // First element less than target is in interval [i, m-1]
+        }
+    }
+    // Return insertion point i
+    return i;
+}
+
+/* Binary search for the leftmost target */
+int binarySearchLeftEdge(vector<int> &nums, int target) {
+    // Equivalent to finding the insertion point of target
+    int i = binarySearchInsertion(nums, target);
+    // Did not find target, thus return -1
+    if (i == nums.size() || nums[i] != target) {
+        return -1;
+    }
+    // Found target, return index i
+    return i;
+}
+
+/* Binary search for the rightmost target */
+int binarySearchRightEdge(vector<int> &nums, int target) {
+    // Convert to finding the leftmost target + 1
+    int i = binarySearchInsertion(nums, target + 1);
+    // j points to the rightmost target, i points to the first element greater than target
+    int j = i - 1;
+    // Did not find target, thus return -1
+    if (j == -1 || nums[j] != target) {
+        return -1;
+    }
+    // Found target, return index j
+    return j;
+}
+
+/* Driver Code */
+int main() {
+    // Array with duplicate elements
+    vector<int> nums = {1, 3, 6, 6, 6, 6, 6, 10, 12, 15};
+    cout << "\nArray nums = ";
+    printVector(nums);
+
+    // Binary search for left and right boundaries
+    for (int target : {6, 7}) {
+        int index = binarySearchLeftEdge(nums, target);
+        cout << "The leftmost index of element " << target << " is " << index << endl;
+        index = binarySearchRightEdge(nums, target);
+        cout << "The rightmost index of element " << target << " is " << index << endl;
+    }
+
+    return 0;
+}