finished cls04

src/cls04/Makefile

@@ -0,0 +1,14 @@
+include ../common.mk
+
+PROJECT_NAME:=cls04
+
+TGTS:=$(patsubst %.c,%,$(wildcard *.c))
+
+all: $(TGTS)
+
+%: %.c
+	@mkdir -p $(BUILD_PATH)/$(PROJECT_NAME)
+	$(CC) $(CFLAGS) -I. $^ -o $(BUILD_PATH)/$(PROJECT_NAME)/$@
+
+clean:
+	$(RM) -drf $(BUILD_PATH)/$(PROJECT_NAME)

src/cls04/a1.c

@@ -0,0 +1,42 @@
+#include <stdio.h>
+
+#include "reduce.h"
+#include "utils.h"
+
+int addFrac(int x[], int y[]) {
+    if (x[1] == 0 || y[1] == 0) {
+        return -1;
+    }
+
+    int l = lcm(x[1], y[1]);
+    int z[] = {
+        (x[0] * l)/x[1] + (y[0] * l)/y[1],
+        l
+    };
+
+    reduce(z);
+    formatNeg(z);
+
+    x[0] = z[0];
+    x[1] = z[1];
+    return 0;
+}
+
+int main(void) {
+    int x[2] = {0};
+    int y[2] = {0};
+
+    inputFrac(x);
+    inputFrac(y);
+
+    int ret = addFrac(x, y);
+
+    if (ret == 0) {
+        printFrac(x);
+        putchar('\n');
+    } else {
+        fprintf(stderr, "Error: detected zero div\n");
+    }
+
+    return 0;
+}

src/cls04/a2.c

@@ -0,0 +1,43 @@
+#include <stdio.h>
+
+#include "reduce.h"
+#include "utils.h"
+
+int subFrac(int x[], int y[]) {
+    if (x[1] == 0 || y[1] == 0) {
+        return -1;
+    }
+
+    int l = lcm(x[1], y[1]);
+    int z[] = {
+        (x[0] * l)/x[1] - (y[0] * l)/y[1],
+        l
+    };
+
+    reduce(z);
+    formatNeg(z);
+
+    x[0] = z[0];
+    x[1] = z[1];
+
+    return 0;
+}
+
+int main(void) {
+    int x[2] = {0};
+    int y[2] = {0};
+
+    inputFrac(x);
+    inputFrac(y);
+
+    int ret = subFrac(x, y);
+
+    if (ret == 0) {
+        printFrac(x);
+        putchar('\n');
+    } else {
+        fprintf(stderr, "Error: detected zero div\n");
+    }
+
+    return 0;
+}

src/cls04/a3.c

@@ -0,0 +1,42 @@
+#include <stdio.h>
+
+#include "reduce.h"
+#include "utils.h"
+
+int mulFrac(int x[], int y[]) {
+    if (x[1]*y[1] == 0) {
+        return -1;
+    }
+
+    int z[] = {
+        x[0] * y[0],
+        x[1] * y[1]
+    };
+
+    reduce(z);
+    formatNeg(z);
+
+    x[0] = z[0];
+    x[1] = z[1];
+
+    return 0;
+}
+
+int main(void) {
+    int x[2] = {0};
+    int y[2] = {0};
+
+    inputFrac(x);
+    inputFrac(y);
+
+    int ret = mulFrac(x, y);
+
+    if (ret == 0) {
+        printFrac(x);
+        putchar('\n');
+    } else {
+        fprintf(stderr, "Error: Detected zero div\n");
+    }
+
+    return 0;
+}

src/cls04/a4.c

@@ -0,0 +1,31 @@
+#include <stdio.h>
+
+int getnum(void) {
+    int ch, n = 0;
+
+    int stack[10] = {0}; // ceil(log_10(2^31))
+    int i = 0;
+    while ((ch = getchar()) != '\n') {
+        int x = ch - '0';
+        if (x < 0 || x > 9) {
+            continue;
+        }
+        if (i <= 9) stack[i++] = x; // stack push
+    }
+
+    int d = 1;
+    for (int j = i - 1; j >= 0; j--) {
+        n += stack[j] * d; // stack pop
+        d = d * 10;
+    }
+
+    return n;
+}
+
+int main(void) {
+    int ret = getnum();
+
+    printf("got: %d\n", ret);
+
+    return 0;
+}

src/cls04/reduce.h

@@ -0,0 +1,28 @@
+#ifndef __REDUCE_H__
+#define __REDUCE_H__
+
+int gcm(int a, int b) {
+    int x = a, y = b;
+    if (x < y) {
+        x = b;
+        y = a;
+    }
+    int r = a % b;
+    if (r == 0) return b;
+    return gcm(b, r);
+}
+
+int lcm(int a, int b) {
+    int g = gcm(a, b);
+    return b * a / g;
+}
+
+void reduce(int x[]) {
+    int a = x[0], b = x[1];
+    int g = gcm(a, b);
+    x[0] = a / g;
+    x[1] = b / g;
+}
+
+
+#endif // __REDUCE_H__

src/cls04/utils.h

@@ -0,0 +1,31 @@
+#ifndef __UTILS_H__
+#define __UTILS_H__
+
+#include <stdio.h>
+
+void inputFrac(int x[]) {
+    printf("Input fraction(a/b): ");
+    scanf("%d/%d", &x[0], &x[1]);
+}
+
+void formatNeg(int x[]) {
+    size_t sz = sizeof(int);
+    int cnt = 0;
+    for (size_t i = 0; i < 2; i++) {
+        cnt += x[i] < 0 ? 1 : 0;
+        x[i] = x[i] < 0 ? x[i] * -1 : x[i];
+    }
+
+    if (cnt == 1)
+        x[0] = -1 * x[0];
+}
+
+void printFrac(int x[]) {
+    if (x[1] == 1) {
+        printf("%d", x[0]);
+    } else {
+        printf("%d/%d", x[0], x[1]);
+    }
+}
+
+#endif // __UTILS_H__