From 235484859ebf77d129534903cbad0959d0a61bbc Mon Sep 17 00:00:00 2001
From: juan <juancloudcomputing@protonmail.com>
Date: Mon, 1 Nov 2021 20:25:24 +0800
Subject: [PATCH] add 1 to 4

---
 pset6/1-soldiers.c | 34 ++++++++++++++++++++++++++++++++++
 pset6/2-circle.c   | 22 ++++++++++++++++++++++
 pset6/3-reverse.c  | 43 +++++++++++++++++++++++++++++++++++++++++++
 pset6/4-binary.c   | 33 +++++++++++++++++++++++++++++++++
 4 files changed, 132 insertions(+)
 create mode 100644 pset6/1-soldiers.c
 create mode 100644 pset6/2-circle.c
 create mode 100644 pset6/3-reverse.c
 create mode 100644 pset6/4-binary.c

diff --git a/pset6/1-soldiers.c b/pset6/1-soldiers.c
new file mode 100644
index 0000000..11171b1
--- /dev/null
+++ b/pset6/1-soldiers.c
@@ -0,0 +1,34 @@
+#include <stdio.h>
+
+int main(void) {
+  // Initialize variables
+  int n;
+  scanf("%d", &n);
+
+  // Start looping
+  int sum;
+	int found = 0;
+  for (int a = 0; found != 1; a++) {
+    sum = a * 5 + 1;
+    for (int b = 0; sum >= b * 6 + 5; b++) {
+      if (sum != b * 6 + 5) { // The sum don't equal
+        continue;
+      }
+      for (int c = 0; sum >= 7 * c + 6; c++) {
+        if (sum != 7 * c + 6) {
+          continue;
+        }
+        for (int d = 0; sum >= 11 * d + 10; d++) {
+          if (sum != 11 * d + 10) {
+            continue;
+          }
+          if (sum >= n) {
+            printf("%i\n", sum);
+						found = 1;
+          }
+        }
+      }
+    }
+  }
+  return 0;
+}
diff --git a/pset6/2-circle.c b/pset6/2-circle.c
new file mode 100644
index 0000000..7b07e5d
--- /dev/null
+++ b/pset6/2-circle.c
@@ -0,0 +1,22 @@
+#include <stdio.h>
+
+// Function prototypes
+int calculate(int a);
+
+int main(void) {
+  // Initialize variables
+  int n;
+  scanf("%i", &n);
+
+	// Calculate answer
+	printf("%i\n", calculate(n));
+  return 0;
+}
+
+int calculate(int a) {
+	if (a == 0) {
+		return 1;
+	} else {
+		return calculate(a - 1) - a + a * 2;
+	}
+}
diff --git a/pset6/3-reverse.c b/pset6/3-reverse.c
new file mode 100644
index 0000000..f9c8dc9
--- /dev/null
+++ b/pset6/3-reverse.c
@@ -0,0 +1,43 @@
+#include <stdio.h>
+
+// Function prototypes
+int get_length(int n);
+int get_last(int n, int loc);
+
+int main(void) {
+  // Initialize variables
+  int n;
+  scanf("%d", &n);
+
+  int len = get_length(n);
+  /* printf("%i\n", len); */
+  for (int i = 1; i <= len / 2; i++) {
+    if (get_last(n, len - i + 1) != get_last(n, i)) {
+      /* printf("the number at %i is %i\n", i, get_last(n, i)); */
+      /* printf("the number at %i is %i\n", len - i, get_last(n, len - i + 1)); */
+      printf("No\n");
+      return 0;
+    }
+  }
+  printf("Yes\n");
+  return 0;
+}
+
+int get_length(int n) {
+  int len = 0;
+  if (n == 0) { // 0 should have the same digits as 1 - 9
+    n = 9;
+  }
+  while (n > 0) {
+    n /= 10;
+    len++;
+  }
+  return len;
+}
+
+int get_last(int n, int loc) {
+  for (int i = 1; i < loc; i++) {
+    n /= 10;
+  }
+  return n % 10;
+}
diff --git a/pset6/4-binary.c b/pset6/4-binary.c
new file mode 100644
index 0000000..6081cf2
--- /dev/null
+++ b/pset6/4-binary.c
@@ -0,0 +1,33 @@
+#include <stdio.h>
+
+// Function prototypes
+int bin2dec(int n);
+int pow2(int n);
+
+int main(void) {
+  // Initialize variables
+  int n;
+  scanf("%d", &n);
+
+  printf("%d\n", bin2dec(n));
+  return 0;
+}
+
+int bin2dec(int n) {
+  int ans = 0;
+  int loc = 0;
+  while (n != 0) {
+    ans += pow2(loc) * (n % 10);
+    n /= 10;
+    loc++;
+  }
+  return ans;
+}
+
+int pow2(int n) {
+  int ans = 1;
+  for (int i = 0; i < n; i++) {
+    ans *= 2;
+  }
+  return ans;
+}