From 1d1f778fa1a50385cbbed370b41f7af0784f50b6 Mon Sep 17 00:00:00 2001
From: Wu Mianzhi <10215501411@stu.ecnu.edu.cn>
Date: Fri, 16 Sep 2022 19:30:55 +0800
Subject: [PATCH] finish quiz5-6

---
 lab2/datalab-handout/bits.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/lab2/datalab-handout/bits.c b/lab2/datalab-handout/bits.c
index 7be88d5..c9bb625 100644
--- a/lab2/datalab-handout/bits.c
+++ b/lab2/datalab-handout/bits.c
@@ -206,7 +206,9 @@ int allOddBits(int x) {
  *   Rating: 2
  */
 int negate(int x) {
-  return 2;
+  int notx = ~x;
+  int res = notx + 1;// since ~x + x = 1111...111 = -1, ~x + x + 1 = 0
+  return res;
 }
 //3
 /* 
@@ -219,7 +221,12 @@ int negate(int x) {
  *   Rating: 3
  */
 int isAsciiDigit(int x) {
-  return 2;
+  int neg0x3a = ~(0x3a) + 1;
+  int neg0x30 = ~(0x30) + 1;
+  int signofminus0x3a = (x + neg0x3a) >> 31; // should be all 1
+  int signofminus0x30 = (x + neg0x30) >> 31; // should be all 0
+  int res = !(signofminus0x30 | (~signofminus0x3a));
+  return res;
 }
 /* 
  * conditional - same as x ? y : z