finished Chapter-3

Author: satyajitghana

Chapter-3/Exercise 3-4/itoa.c

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+#include <stdio.h>
+#include <string.h>
+#include <limits.h>
+#define MAXLENGTH 100
+
+void itoa(int number, char string[]);
+void reverse(char str[]);
+
+int main() {
+    char buffer[MAXLENGTH];
+    int num = INT_MIN;
+    itoa(num, buffer);
+    printf("%s\n", buffer);
+    return 0;
+}
+
+void itoa(int n, char s[]) {
+    int i, sign = 1;
+    unsigned num;
+    if(n < 0) {num = -n; sign = -1;}
+    i = 0;
+    do {
+        s[i++] = num % 10 + '0';
+    } while ((num /= 10) > 0);
+    
+    if (sign < 0) s[i++] = '-';
+    s[i] = '\0';
+    reverse(s);
+}
+
+void reverse(char s[]) {
+    int c, i, j;
+    for (i = 0, j = strlen(s)-1; i < j ; i++, j--) {
+        c = s[j], s[j] = s[i], s[i] = c;
+    }
+}

Chapter-3/Exercise 3-4/itoa_v2.c

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+#include <stdio.h>
+#include <string.h>
+#include <limits.h>
+#include <stdlib.h>
+#define MAXLENGTH 100
+
+void itoa(int number, char string[]);
+void reverse(char str[]);
+
+int main() {
+    char buffer[MAXLENGTH];
+    int num = INT_MIN;
+    itoa(num, buffer);
+    printf("%s\n", buffer);
+    return 0;
+}
+
+void itoa(int n, char s[]) {
+    int i, sign;
+    sign = n;
+    i = 0;
+    do {
+        s[i++] = abs(n % 10) + '0';
+    } while (n /= 10);
+    
+    if (sign < 0) s[i++] = '-';
+    s[i] = '\0';
+    reverse(s);
+}
+
+void reverse(char s[]) {
+    int c, i, j;
+    for (i = 0, j = strlen(s)-1; i < j ; i++, j--) {
+        c = s[j], s[j] = s[i], s[i] = c;
+    }
+}

Chapter-3/Exercise 3-5/itob.c

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+#include <stdio.h>
+#include <string.h>
+#include <limits.h>
+#define MAXLENGTH 1000
+
+int itob(int num, char str[], int base);
+void reverse(char string[]);
+
+int main() {
+    char encoded[MAXLENGTH];
+    int num = INT_MAX;
+    int base = 62;
+    if (itob(num, encoded, base) != -1) printf("%s\n", encoded);
+    return 0;
+}
+
+int itob(int n, char s[], int b) {
+    static const char CHARS[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
+    if (b < 2 || b > 62) return -1;
+    int i = 0;
+    do {
+        s[i++] = CHARS[n % b];
+    } while (n /= b);
+    s[i] = '\0';
+    reverse(s);
+}
+
+void reverse(char s[]) {
+    int c, i, j;
+    for (i = 0, j = strlen(s)-1; i < j ; i++, j--) {
+        c = s[j], s[j] = s[i], s[i] = c;
+    }
+}

Chapter-3/Exercise 3-6/itoa.c

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+#include <stdio.h>
+#include <string.h>
+#include <limits.h>
+#include <stdlib.h>
+#define MAXLENGTH 100
+
+void itoa(int number, char string[], int field_width);
+void reverse(char str[]);
+
+int main() {
+    char buffer[MAXLENGTH];
+    int num = INT_MIN;
+    int width = 15;
+    itoa(num, buffer, width);
+    printf("%s\n", buffer);
+    return 0;
+}
+
+void itoa(int n, char s[], int w) {
+    int i, sign;
+    sign = n;
+    i = 0;
+    do {
+        s[i++] = abs(n % 10) + '0';
+    } while (n /= 10);
+    
+    if (sign < 0) s[i++] = '-';
+    while (w - i > 0) s[i++] = ' ';
+    s[i] = '\0';
+    reverse(s);
+}
+
+void reverse(char s[]) {
+    int c, i, j;
+    for (i = 0, j = strlen(s)-1; i < j ; i++, j--) {
+        c = s[j], s[j] = s[i], s[i] = c;
+    }
+}