From 954a05320003f84586c94a526de78f9ca620e45c Mon Sep 17 00:00:00 2001
From: juan <juancloudcomputing@protonmail.com>
Date: Thu, 2 Dec 2021 19:05:51 +0800
Subject: [PATCH] add binsearches

---
 pset10/6-BinarySearchIteration.c | 46 ++++++++++++++++++++++++++++++++
 pset10/6-binsearch.c             |  0
 pset10/7-BinarySearchRecursion.c | 45 +++++++++++++++++++++++++++++++
 3 files changed, 91 insertions(+)
 create mode 100644 pset10/6-BinarySearchIteration.c
 delete mode 100644 pset10/6-binsearch.c
 create mode 100644 pset10/7-BinarySearchRecursion.c

diff --git a/pset10/6-BinarySearchIteration.c b/pset10/6-BinarySearchIteration.c
new file mode 100644
index 0000000..7441d7e
--- /dev/null
+++ b/pset10/6-BinarySearchIteration.c
@@ -0,0 +1,46 @@
+#include <stdio.h>
+
+//函数功能：二分查找
+//函数参数：分别为被查找的数组，数组长度，所查找的元素
+//函数返回值：如果找到，则返回该元素在数组中的下标，否则返回-1
+int BinarySearch(int a[], int n, int key);
+
+int main() {
+  int num
+      [2000000]; //这个数组比较大，如果在你的电脑中无法分配这么大的内存，请改小后测试。
+  int n, m, i;
+  int key;
+
+  scanf("%d%d", &n, &m);
+  for (i = 0; i < n; i++)
+    scanf("%d", &num[i]);
+
+  for (i = 0; i < m; i++) {
+    scanf("%d", &key);
+    printf("%d", BinarySearch(num, n, key));
+    if (i != m - 1)
+      printf(" ");
+    else
+      printf("\n");
+  }
+  return 0;
+}
+
+/* 请在这里填写答案 */
+int BinarySearch(int a[], int n, int key) {
+  int mid;
+  int l = 0, r = n - 1;
+  while (r >= l) {
+    mid = (l + r) / 2;
+    if (a[mid] == key) {
+      return mid;
+    } else if (a[mid] > key) {
+      // Search left
+      r = mid - 1;
+    } else {
+      // search right
+      l = mid + 1;
+    }
+ }
+  return -1;
+}
diff --git a/pset10/6-binsearch.c b/pset10/6-binsearch.c
deleted file mode 100644
index e69de29..0000000
diff --git a/pset10/7-BinarySearchRecursion.c b/pset10/7-BinarySearchRecursion.c
new file mode 100644
index 0000000..17d9a5c
--- /dev/null
+++ b/pset10/7-BinarySearchRecursion.c
@@ -0,0 +1,45 @@
+#include <stdio.h>
+
+#define MAXN 2000000
+
+int RecurBinarySearch(int a[], int key, int left, int right);
+
+int main() {
+  int a
+      [MAXN]; //这个数组比较大，如果在你的电脑中无法分配这么大的内存，请改小后测试。
+  int n, m, i, key;
+
+  scanf("%d %d", &n, &m);
+  for (i = 0; i < n; i++)
+    scanf("%d", &a[i]);
+
+  for (i = 0; i < m; i++) {
+    scanf("%d", &key);
+    printf("%d", RecurBinarySearch(a, key, 0, n - 1));
+    if (i != m - 1)
+      printf(" ");
+    else
+      printf("\n");
+  }
+
+  return 0;
+}
+
+/* 请在这里填写答案 */
+// --last hope--
+#pragma GCC optimize("Ofast,inline")          // "Ofast" = "O3,fast-math,allow-store-data-races,no-protect-parens"
+int RecurBinarySearch(int a[], int key, int left, int right) {
+	if (left <= right) {
+		int mid = (left + right) >> 1;
+		if (a[mid] == key) { // Base case
+			return mid;
+		} else if (a[mid] > key) {
+			// Search left
+			return RecurBinarySearch(a, key, left, mid - 1);
+		} else {
+			return RecurBinarySearch(a, key, mid + 1, right);
+		}
+	} else {
+		return -1;
+	}
+}