June 2018 Update

Task/Binary-search/C++/binary-search-1.cpp

@@ -1,24 +1,22 @@
-template <class T>
-int binsearch(const T array[], int len, T what)
-{
-  if (len == 0) return -1;
-  int mid = len / 2;
-  if (array[mid] == what) return mid;
-  if (array[mid] < what) {
-    int result = binsearch(array+mid+1, len-(mid+1), what);
-    if (result == -1) return -1;
-    else return result + mid+1;
-  }
-  if (array[mid] > what)
-    return binsearch(array, mid, what);
+template <class T> int binsearch(const T array[], int low, int high, T value) {
+    if (high < low) {
+        return -1;
+    }
+    auto mid = (low + high) / 2;
+    if (value < array[mid]) {
+        return binsearch(array, low, mid - 1, value);
+    } else if (value > array[mid]) {
+        return binsearch(array, mid + 1, high, value);
+    }
+    return mid;
 }
 
 #include <iostream>
 int main()
 {
   int array[] = {2, 3, 5, 6, 8};
-  int result1 = binsearch(array, sizeof(array)/sizeof(int), 4),
-      result2 = binsearch(array, sizeof(array)/sizeof(int), 8);
+  int result1 = binsearch(array, 0, sizeof(array)/sizeof(int), 4),
+      result2 = binsearch(array, 0, sizeof(array)/sizeof(int), 8);
   if (result1 == -1) std::cout << "4 not found!" << std::endl;
   else std::cout << "4 found at " << result1 << std::endl;
   if (result2 == -1) std::cout << "8 not found!" << std::endl;

Task/Binary-search/Julia/binary-search-1.julia

@@ -1,15 +1,15 @@
-function binary_search(l, value)
+function binarysearch(lst::Vector{T}, val::T) where T
     low = 1
-    high = length(l)
-    while low <= high
-        mid = int((low+high)/2)
-        if l[mid] > value
-          high = mid-1
-        elseif l[mid] < value
-          low = mid+1
+    high = length(lst)
+    while low ≤ high
+        mid = (low + high) ÷ 2
+        if lst[mid] > val
+            high = mid - 1
+        elseif lst[mid] < val
+            low = mid + 1
         else
-          return mid
+            return mid
         end
     end
-      return -1
+    return 0
 end

Task/Binary-search/Julia/binary-search-2.julia

@@ -1,10 +1,18 @@
-function binary_search(l, value, low = 1, high = -1)
-  high == -1    &&  (high = length(l))
-  l==[]         &&  (return -1)
-  low >= high   &&
-    ((low > high || l[low] != value) ? (return -1) : return low)
-  mid = int((low+high)/2)
-  l[mid] > value ? (return binary_search(l, value, low, mid-1))  :
-    l[mid] < value ? (return binary_search(l, value, mid+1, high)) :
-      return mid
+function binarysearch(lst::Vector{T}, value::T, low=1, high=length(lst)) where T
+    if isempty(lst) return 0 end
+    if low ≥ high
+        if low > high || lst[low] != value
+            return 0
+        else
+            return low
+        end
+    end
+    mid = (low + high) ÷ 2
+    if lst[mid] > value
+        return binarysearch(lst, value, low, mid-1)
+    elseif lst[mid] < value
+        return binarysearch(lst, value, mid+1, high)
+    else
+        return mid
+    end
 end

Task/Binary-search/N-t-roff/binary-search.n

@@ -0,0 +1,38 @@
+.de end
+..
+.de array
+.	nr \\$1.c 0 1
+.	de \\$1.push end
+.		nr \\$1..\\\\n+[\\$1.c] \\\\$1
+.	end
+.	de \\$1.pushln end
+.		if \\\\n(.$>0 .\\$1.push \\\\$1
+.		if \\\\n(.$>1 \{ \
+.			shift
+.			\\$1.pushln \\\\$@
+\}
+.	end
+..
+.
+.de binarysearch
+.	nr min 1
+.	nr max \\n[\\$1.c]
+.	nr guess \\n[min]+\\n[max]/2
+.	while !\\n[\\$1..\\n[guess]]=\\$2 \{ \
+.		ie \\n[\\$1..\\n[guess]]<\\$2 .nr min \\n[guess]+1
+.		el .nr max \\n[guess]-1
+.
+.		if \\n[min]>\\n[max] \{
+.			nr guess 0
+.			break
+.		\}
+.		nr guess \\n[min]+\\n[max]/2
+.	\}
+\\n[guess]
+..
+.array a
+.a.pushln 1 4 9 16 25 36 49 64 81 100 121 144
+.binarysearch a 100
+.br
+.ie \n[guess]=0 The item \fBdoesn't exist\fP.
+.el The item \fBdoes exist\fP.

Task/Binary-search/PARI-GP/binary-search-2.pari

@@ -0,0 +1,24 @@
+binarysearch(v, x) = {
+    local(
+        minm = 1,
+        maxm = length(v),
+        guess = floor(maxm/2+minm/2)
+    );
+
+    while(v[guess] != x,
+        if(v[guess] < x, minm = guess + 1, maxm = guess - 1);
+        if(minm > maxm,
+            guess = 0;
+            break
+        );
+        guess = floor(maxm/2+minm/2)
+    );
+
+    return(guess);
+}
+
+idx = binarysearch([1,4,9,16,25,36,49,64,81,100,121,144], 121);
+if(idx, \
+    print("Item exists on index ", idx), \
+    print("Item does not exist anywhere.") \
+)

Task/Binary-search/Rust/binary-search-1.rust

@@ -0,0 +1,3 @@
+let arr = ["a", "bc", "def", "ghij"];
+arr.binary_search(&"a"); // Search lexicographically
+arr.binary_search_by(|e| e.len().cmp(&1)); // Search by length

Task/Binary-search/Rust/binary-search-2.rust

@@ -0,0 +1,18 @@
+use std::cmp::Ordering::*;
+fn binary_search<T: Ord>(arr: &[T], elem: &T) -> Option<usize>
+{
+    let mut size = arr.len();
+    let mut base = 0;
+
+    while size > 0 {
+        size /= 2;
+        let mid = base + size;
+        base = match arr[mid].cmp(elem) {
+            Less    => mid,
+            Greater => base,
+            Equal   => return Some(mid)
+        };
+    }
+
+    None
+}

Task/Binary-search/Rust/binary-search.rust

@@ -1,17 +0,0 @@
-fn bin_search<T : PartialOrd>(sar : &[T], v : &T) -> Option<usize> {
-    let mut lowi=0;
-    let mut highi=sar.len();
-    loop {
-        if lowi>=highi {
-            return None;
-        }
-        let mi=lowi+(highi-lowi)/2;
-        if sar[mi].lt(v) {
-            lowi=mi+1;
-        } else if sar[mi].gt(v) {
-            highi=mi;
-        } else {
-            return Some(mi);
-        }
-    }
-}