c practices level1 -- 孔淳漳

practices/c/level1/p01_runningLetter/p01_Runningletter.cpp

@@ -0,0 +1,34 @@
+#include <stdio.h>
+#include <string.h>
+#include <windows.h>
+
+int main()
+{
+    char c;
+    scanf ("%c", &c);
+    int i,j;
+    system("mode con cols=16 lines=9");
+    int width = GetSystemMetrics ( SM_CXSCREEN );
+    for (i = 0; i < 16; i++)
+    {
+        system ("cls");
+        for (j = 0; j < i; j++)
+        {
+            printf (" ");
+        }
+        printf ("%c", c);
+        Sleep (100);
+    }
+    for(i = 15; i >= 0; i--)
+    {
+    	system ("cls");
+    	for (j = 0; j < i; j++)
+    	{
+		    printf (" ");
+		}
+		printf ("%c", c);
+		Sleep (100);
+		printf ("\n");
+	}
+    return 0;
+}

practices/c/level1/p02_isPrime/p02_isPrime.cpp

@@ -0,0 +1,17 @@
+#include<stdio.h>
+
+int main(void)
+{
+	int i, n;
+	scanf ("%d", &n);
+	for (i = 2; i < n; i++)
+	{
+		if(n % i == 0)
+		break;
+	}
+	if(i == n)
+	printf ("%d is a prime\n", n);
+	else
+	printf ("%d isn't a prime\n", n);
+	return 0; 
+} 

practices/c/level1/p03_Diophantus/p03_Diophantus.cpp

@@ -0,0 +1,15 @@
+#include<stdio.h>
+
+int main(void)
+{
+	float i;
+	for(i = 0; i < 150; i++)
+	{
+		if((i / 6 + i / 12 + i / 7 + 5 + i / 2 + 4) == i)
+		{
+		    printf ("When Diophantus's son dead, Diophantus's age is %g", i - 4);
+		    break;
+	    }
+	}
+	return 0;
+} 

practices/c/level1/p04_ narcissus/p04_Narcissus.cpp

@@ -0,0 +1,15 @@
+#include<stdio.h>
+#include<math.h>
+
+int main(void)
+{
+	int i;
+	for (i=100; i < 1000; i++)
+	{
+		if (pow (i / 100, 3) + pow((i % 100) / 10, 3) + pow(i % 10, 3) == i)
+		{
+			printf("%d\n", i);
+		}
+	}
+	return 0;
+}

practices/c/level1/p05_allPrimes/p05_allprimes.cpp

@@ -0,0 +1,34 @@
+#include<stdio.h>
+#include<string.h>
+#include<time.h>
+#define N 1000001
+
+int main()
+{
+	float start, finish;
+	start = clock();
+	bool prime[N];
+	memset(prime, true, sizeof(prime));
+	prime[0] = prime[1] = false;
+	for(int i = 2; i < N; i++)
+	{
+		if(prime[i])
+		for(int j = i * 2; j < N; j += i)
+		{
+			prime[j] = false;
+		}
+	}
+	FILE * fp;
+	//fp = fopen("allprime.txt", "w");
+	freopen("allprime.txt", "w", stdout);
+	for(int k = 0; k <N; k++)
+	{
+		if(prime[k])
+			printf("%d ", k);
+		//fprintf(fp, "%d ", k);
+	}
+	finish = clock();
+	printf("\n%g\n", (finish - start) / CLOCKS_PER_SEC);
+	//fclose(fp);
+	return 0;
+}

practices/c/level1/p06_Goldbach/p06_Goldbach.cpp

@@ -0,0 +1,32 @@
+#include<stdio.h>
+
+int isprime(int i);
+int main()
+{
+	int x, y;
+	for(x = 4; x < 101; x += 2)
+	{
+		for(y = 2; y <= x / 2; y++)
+		{
+			if(isprime(y) != 0)
+				if(isprime(x - y) != 0)
+					printf("%d = %d + %d\n", x, y, x - y);
+		}
+	}
+	printf("Proof done.\n");
+	return 0;
+}
+
+int isprime(int i)
+{
+	int j;
+	for(j = 2; j < i; j++)
+	{
+		if(i % j == 0)
+			break;
+	}
+	if(i == j)
+		return 1;
+	else
+		return 0;
+}

practices/c/level1/p07_encrypt_decrypt/p07_encrypt_decrypt.cpp

@@ -0,0 +1,37 @@
+#include<stdio.h>
+#include<string.h>
+
+int main()
+{
+	int i, n, command;
+	char text[256] = {'\0'}, encryption[256] = {'\0'};  
+	printf("Plz enter your command.\n");
+	printf("1.Encrypt\n");
+	printf("2.Decrypt\n");
+	printf("3.Exit\n");
+	scanf("%d", &command);
+	if(command == 1)
+	{
+		printf("Plz enter the words you want to encrypt.\n");
+		scanf("%s", &text);
+		n = strlen(text);
+		for(i = 0; i < n; i++)
+		encryption[i] = text[i] + i + 6;
+		encryption[i] = '\0';
+		printf("Encrypt words are %s.\n", encryption);
+	}
+	else if(command == 2)
+	{
+		printf("Plz enter the words you want to decrypt.\n");
+		scanf("%s", &encryption);
+		n = strlen(encryption);
+		for(i = 0; i < n; i++)
+		text[i] = encryption[i] - i - 6;
+		text[i] = '\0';
+		printf("Decrypt words are %s.\n", text);
+	}
+	else if(command == 3)
+	return 0;
+	else
+	printf("Wrong command,plz try again.\n");
+}