Lesson 6

06/Exercise01.c

@@ -0,0 +1,28 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include <math.h>
+
+bool isPrime(int toBeTested){
+    int iterationMax = 0, nowCheck = 2;
+    bool isPrime = true;
+    iterationMax = sqrt(toBeTested);
+    do {
+        if (toBeTested % nowCheck == 0) {
+            isPrime = false;
+            break;
+        }
+        nowCheck++;
+    }
+    while (nowCheck <= iterationMax);
+    return isPrime;
+}
+
+int main() {
+    int j;
+    for (j = 11; j < 198; j+2) {
+        if(isPrime(j) && isPrime(j+2)) {
+            printf("%d %d\n", j, j+2);
+        }
+    }
+    return 0;
+}

06/Exercise02.c

@@ -0,0 +1,35 @@
+#include <stdio.h>
+
+int main() {
+    int n, astCount, spaceCount, outAstCount, outSpaceCount;
+    scanf("%d", &n);
+    spaceCount = (n-1)/2;
+    if (n > 2 && n % 2 == 1) {
+        for(astCount = 1; astCount <= n; astCount+=2){
+            for (outSpaceCount = 0; outSpaceCount < spaceCount; outSpaceCount++) {
+                printf(" ");
+            }
+            for (outAstCount = 0; outAstCount < astCount; outAstCount++) {
+                printf("*");
+            }
+            printf("\n");
+            spaceCount--;
+        }
+        astCount = n-2;
+        spaceCount = 1;
+        for(; astCount > 0; astCount-=2) {
+            for (outSpaceCount = 0; outSpaceCount < spaceCount; outSpaceCount++) {
+                printf(" ");
+            }
+            for (outAstCount = 0; outAstCount < astCount; outAstCount++) {
+                printf("*");
+            }
+            printf("\n");
+            spaceCount++;
+        }
+    }
+    else{
+        printf("input error");
+    }
+    return 0;
+}

06/Exercise03.c

@@ -0,0 +1,35 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include <math.h>
+
+bool isPrime(int toBeTested){
+    int iterationMax = 0, nowCheck = 2;
+    bool isPrime = true;
+    iterationMax = sqrt(toBeTested);
+    do {
+        if (toBeTested % nowCheck == 0) {
+            isPrime = false;
+            break;
+        }
+        nowCheck++;
+    }
+    while (nowCheck <= iterationMax);
+    return isPrime;
+}
+
+int main() {
+    int n, p1;
+    scanf("%d", &n);
+    if (n < 4 || n % 2 == 1) {
+        printf("input error");
+    }
+    else {
+        for (p1=3;;p1+=2) {
+            if (isPrime(p1) && isPrime(n - p1)) {
+                printf("%d = %d + %d", n, p1, n-p1);
+                break;
+            }
+        }
+    }
+    return 0;
+}

06/Optional01.c

@@ -0,0 +1,12 @@
+#include <stdio.h>
+
+int main() {
+    int apple[6] = {0};
+    int childCount = 4;
+    apple[5] = 11;
+    for (;childCount > 0; childCount--) {
+        apple[childCount] = (apple[childCount+1] * (childCount + 1) + 1)/childCount;
+    }
+    printf("Total number of apple: %d\n 1: %d\n 2: %d\n 3: %d\n 4: %d\n 5: %d\n", apple[1], apple[1]-apple[2], apple[2]-apple[3], apple[3]-apple[4], apple[4]-apple[5], apple[5]);
+    return 0;
+}

06/Optional02.c

@@ -0,0 +1,21 @@
+#include <stdio.h>
+
+int factorials[10] = {0};
+
+int factorial(int n) {
+    if (factorials[n-1] == 0) {
+        factorials[n-1] = n * factorial(n-1);
+    }
+    return factorials[n-1];
+}
+
+int main() {
+    int k = 0, sum = 0, i;
+    scanf("%d", &k);
+    factorials[0] = 1;
+    for (i = 1;i <= k; i++) {
+        sum += factorial(i);
+    }
+    printf("%d", sum);
+    return 0;
+}

06/Optional03.c

@@ -0,0 +1,37 @@
+#include <stdio.h>
+
+int main() {
+    int root = 2;// 若一个数有奇数个因子，那么它一定是平方数
+    int possibleFactor = 0;
+    int factorCount = 0;
+    int factors[5] = {0};
+    int testee = 0;
+    factors[0] = 1;
+    printf("1~1000内只包含5个因子的数是:\n");
+    for (;root < 32; root++) {
+        //31^2 < 1000 ^ 32^2，只用考虑到31
+        testee = root*root;
+        factorCount = 0;
+
+        factors[2] = root;
+        factors[4] = testee;
+
+        for (possibleFactor = 2; (possibleFactor < root); possibleFactor++) {
+            if (testee % possibleFactor == 0) {
+                if (factorCount == 0) {
+                    factors[1] = possibleFactor;
+                    factors[3] = testee / possibleFactor;
+                    factorCount++;
+                }
+                else {
+                    factorCount++;
+                    break;
+                }
+            }
+        }
+        if (factorCount == 1) {
+            printf("%3d: %4d%4d%4d%4d%4d\n",testee, factors[0], factors[1], factors[2], factors[3], factors[4]);
+        }
+    }
+    return 0;
+}

06/Optional04.c

@@ -0,0 +1,35 @@
+#include <stdio.h>
+
+int hats[6] = {0};
+int count = 0;
+
+void nextChild(int childIndex, int whiteRemaining, int blackremaining) {
+    int i;
+    if (childIndex == 6) {
+        count++;
+        for (int i = 0; i < 6; i++) {
+            if (hats[i] == -1) {
+                printf("White");
+            }
+            else {
+                printf("Black");
+            }
+            printf("\t");
+        }
+        printf("\n");
+    }
+    if (whiteRemaining > 0) {
+        hats[childIndex] = -1;
+        nextChild(childIndex + 1, whiteRemaining - 1, blackremaining);
+    }
+    if (blackremaining > 0) {
+        hats[childIndex] = 1;
+        nextChild(childIndex + 1, whiteRemaining, blackremaining - 1);
+    }
+}
+
+int main() {
+    nextChild(0, 3, 3);
+    printf("Total: %d", count);
+    return 0;
+}

06/test.c

@@ -0,0 +1,11 @@
+#include <stdio.h>
+
+int main() {
+    int i = 0;
+    do {
+        printf("%d",i);
+        i++;
+    }
+    while (i < 5);
+    return 0;
+}