Data commit

Task/Balanced-ternary/C/balanced-ternary.c

@@ -0,0 +1,202 @@
+#include <stdio.h>
+#include <string.h>
+
+void reverse(char *p) {
+    size_t len = strlen(p);
+    char *r = p + len - 1;
+    while (p < r) {
+        *p ^= *r;
+        *r ^= *p;
+        *p++ ^= *r--;
+    }
+}
+
+void to_bt(int n, char *b) {
+    static char d[] = { '0', '+', '-' };
+    static int v[] = { 0, 1, -1 };
+
+    char *ptr = b;
+    *ptr = 0;
+
+    while (n) {
+        int r = n % 3;
+        if (r < 0) {
+            r += 3;
+        }
+
+        *ptr = d[r];
+        *(++ptr) = 0;
+
+        n -= v[r];
+        n /= 3;
+    }
+
+    reverse(b);
+}
+
+int from_bt(const char *a) {
+    int n = 0;
+
+    while (*a != '\0') {
+        n *= 3;
+        if (*a == '+') {
+            n++;
+        } else if (*a == '-') {
+            n--;
+        }
+        a++;
+    }
+
+    return n;
+}
+
+char last_char(char *ptr) {
+    char c;
+
+    if (ptr == NULL || *ptr == '\0') {
+        return '\0';
+    }
+
+    while (*ptr != '\0') {
+        ptr++;
+    }
+    ptr--;
+
+    c = *ptr;
+    *ptr = 0;
+    return c;
+}
+
+void add(const char *b1, const char *b2, char *out) {
+    if (*b1 != '\0' && *b2 != '\0') {
+        char c1[16];
+        char c2[16];
+        char ob1[16];
+        char ob2[16];
+        char d[3] = { 0, 0, 0 };
+        char L1, L2;
+
+        strcpy(c1, b1);
+        strcpy(c2, b2);
+        L1 = last_char(c1);
+        L2 = last_char(c2);
+        if (L2 < L1) {
+            L2 ^= L1;
+            L1 ^= L2;
+            L2 ^= L1;
+        }
+
+        if (L1 == '-') {
+            if (L2 == '0') {
+                d[0] = '-';
+            }
+            if (L2 == '-') {
+                d[0] = '+';
+                d[1] = '-';
+            }
+        }
+        if (L1 == '+') {
+            if (L2 == '0') {
+                d[0] = '+';
+            }
+            if (L2 == '-') {
+                d[0] = '0';
+            }
+            if (L2 == '+') {
+                d[0] = '-';
+                d[1] = '+';
+            }
+        }
+        if (L1 == '0') {
+            if (L2 == '0') {
+                d[0] = '0';
+            }
+        }
+
+        add(c1, &d[1], ob1);
+        add(ob1, c2, ob2);
+        strcpy(out, ob2);
+
+        d[1] = 0;
+        strcat(out, d);
+    } else if (*b1 != '\0') {
+        strcpy(out, b1);
+    } else if (*b2 != '\0') {
+        strcpy(out, b2);
+    } else {
+        *out = '\0';
+    }
+}
+
+void unary_minus(const char *b, char *out) {
+    while (*b != '\0') {
+        if (*b == '-') {
+            *out++ = '+';
+            b++;
+        } else if (*b == '+') {
+            *out++ = '-';
+            b++;
+        } else {
+            *out++ = *b++;
+        }
+    }
+    *out = '\0';
+}
+
+void subtract(const char *b1, const char *b2, char *out) {
+    char buf[16];
+    unary_minus(b2, buf);
+    add(b1, buf, out);
+}
+
+void mult(const char *b1, const char *b2, char *out) {
+    char r[16] = "0";
+    char t[16];
+    char c1[16];
+    char c2[16];
+    char *ptr = c2;
+
+    strcpy(c1, b1);
+    strcpy(c2, b2);
+
+    reverse(c2);
+
+    while (*ptr != '\0') {
+        if (*ptr == '+') {
+            add(r, c1, t);
+            strcpy(r, t);
+        }
+        if (*ptr == '-') {
+            subtract(r, c1, t);
+            strcpy(r, t);
+        }
+        strcat(c1, "0");
+
+        ptr++;
+    }
+
+    ptr = r;
+    while (*ptr == '0') {
+        ptr++;
+    }
+    strcpy(out, ptr);
+}
+
+int main() {
+    const char *a = "+-0++0+";
+    char b[16];
+    const char *c = "+-++-";
+    char t[16];
+    char d[16];
+
+    to_bt(-436, b);
+    subtract(b, c, t);
+    mult(a, t, d);
+
+    printf("      a: %14s %10d\n", a, from_bt(a));
+    printf("      b: %14s %10d\n", b, from_bt(b));
+    printf("      c: %14s %10d\n", c, from_bt(c));
+    printf("a*(b-c): %14s %10d\n", d, from_bt(d));
+
+    return 0;
+}