第四章完结

Chapter4/if.c

@@ -0,0 +1,87 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+/**
+ *  score [90-100] A
+ *  score [80-90)  B
+ *  score [70-80)  C
+ *  score [60-70)  D
+ *  score [0-60)   E
+ */
+
+// 闰年的判断：能被4整除但不能被100整除，或者能被400整除
+
+int main()
+{
+
+    int year;
+
+    scanf("%d", &year);
+
+    if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0)
+        printf("%d is leap year.\n", year);
+    else
+        printf("%d is not leap year.\n", year);
+
+#if 0
+    int score;
+
+    printf("Enter a score:[0,100]:\n");
+    scanf("%d", &score);
+
+    if (score < 0 || score > 100)
+    {
+        fprintf(stderr, "Input error!\n");
+        exit(1);
+    }
+
+    if (score > 90)
+        puts("A");
+    else if (score > 80)
+        puts("B");
+    else if (score > 70)
+        puts("C");
+    else if (score > 60)
+        puts("D");
+    else
+        puts("E");
+#endif
+
+#if 0
+    if (score <= 100 && score >= 90)
+        puts("A");
+    if (score <= 90 && score >= 80)
+        puts("B");
+    if (score <= 80 && score >= 70)
+        puts("C");
+    if (score <= 70 && score >= 60)
+        puts("D");
+    if (score <= 60 && score >= 0)
+        puts("E");
+#endif
+
+#if 0
+    int a = 1, b = 1,c=2;
+    if (a == b)
+        if(b==c)
+            printf("a==b\n");
+    else
+        printf("a!=b\n")
+    注意：else看的是最近的if！！！
+#endif
+
+#if 0
+    int a = 9, b = 10;
+
+    if (b++ < a)
+        printf("1\n");
+    else
+        printf("0\n");
+
+    printf("a=%d,b=%d\n", a, b);
+
+    printf("%d\n", (++b < a, ++a, b++));
+#endif
+
+    exit(0);
+}