feat: added ternary search

searches/ternary.search.R

@@ -0,0 +1,53 @@
+#' Performs ternary search on a sorted integer array.
+#'
+#' @param arr Integer vector. Must be sorted in ascending order.
+#' @param target Integer value to search for in arr.
+#' @return The index (1-based) of the target in arr if found, otherwise -1.
+#' @details The input array must be sorted in ascending order for correct results.
+# Ternary Search in R – works on sorted arrays
+
+ternary_search <- function(arr, target) {
+  l <- 1
+  r <- length(arr)
+  while (l <= r) {
+    mid1 <- l + (r - l) %/% 3
+    mid2 <- r - (r - l) %/% 3
+
+    if (arr[mid1] == target) return(mid1)
+    if (arr[mid2] == target) return(mid2)
+
+    if (target < arr[mid1]) {
+      r <- mid1 - 1
+    } else if (target > arr[mid2]) {
+      l <- mid2 + 1
+    } else {
+      l <- mid1 + 1
+      r <- mid2 - 1
+    }
+  }
+  return(-1)
+}
+
+# --- User Input Section with Validation ---
+arr_input <- readline("Enter sorted integers: ")
+arr_split <- strsplit(arr_input, " ")[[1]]
+arr <- as.integer(arr_split)
+if (length(arr) == 0 || any(is.na(arr))) {
+  cat("Error: Please enter a non-empty list of valid integers separated by spaces.\n")
+  quit(status = 1)
+}
+
+target_input <- readline("Enter target to search: ")
+target <- suppressWarnings(as.integer(target_input))
+if (is.na(target_input) || is.na(target)) {
+  cat("Error: Please enter a valid integer for the target.\n")
+  quit(status = 1)
+}
+
+# --- Execute Search ---
+index <- ternary_search(arr, target)
+
+if (index != -1)
+  cat("Element found at position:", index, "\n")
+else
+  cat("Element not found.\n")