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fib.c

@@ -0,0 +1,12 @@
+#include <stdio.h>
+
+int fib(int n) {
+    if (n <= 1) return n;
+    return fib(n - 1) + fib(n - 2);
+}
+
+int main() {
+    int n = 10;
+    printf("%d fib element: %d\n", n, fib(n-1));
+    return 0;
+}

main_prog.c

@@ -0,0 +1,23 @@
+#include <stdio.h>
+
+int foo(int *a, int b){
+
+	printf("foo a %x \n");
+	*a = 1499;
+	return 42;
+}
+int
+main(int argc, const char *argv[]) {
+
+	int arr[3] = {1, 2, 3};
+	printf("arr[1] = %d\n", arr[1]);
+	printf("hello world\n");
+	int *pa;
+	pa = arr;
+	printf("pa[0] = %d\n", pa[0]);
+	return 0;
+
+	int a = 13, b = 37;
+
+	foo(&a, b);
+}

myatoi.c

@@ -0,0 +1,39 @@
+#include <stdio.h>
+#include <ctype.h>
+#include <string.h>
+
+int myatoi(char *instr) {
+    int sign = 1;
+    if (*instr == '-') {
+        sign = -1;
+        instr++;
+    }
+
+    for (; *instr != '\0'; instr++) {
+        if (!isdigit(*instr)) {
+            return 0;
+        }
+    }
+
+    int num = 0;
+    instr -= strlen(instr);
+
+    while (*instr >= '0' && *instr <= '9') {
+        num = num * 10 + (*instr - '0');
+        instr++;
+    }
+
+    return num * sign;
+}
+
+int main() {
+    char input[] = "-2890";
+    int number = myatoi(input);
+    printf("Converted number is: %d\n", number);
+
+    char bad_input[] = "2890kjdfshdfsh";
+    number = myatoi(bad_input);
+    printf("Bad input result: %d\n", number);
+
+    return 0;
+}

mystr_idx.c

@@ -0,0 +1,21 @@
+#include <stdio.h>
+
+int mystr_idx(char *str, char *substr) {
+    for (int i = 0; str[i]; i++) {
+        int j = 0;
+        while (str[i + j] && substr[j] && str[i + j]  == substr[j]) {
+            j++;
+        }
+        if (!substr[j]) {
+            return i;
+        }
+    }
+    return -1;
+}
+int main() {
+    char str[] = "Hello, world!";
+    char substr[] = "world";
+    int index = mystr_idx(str, substr);
+    printf("substring index '%s' in string '%s': %d\n", substr, str, index);
+    return 0;
+}

mystrlen.c

@@ -0,0 +1,16 @@
+#include <stdio.h>
+
+void mystrlen(const char *s) {
+    int length = 0;
+    while (s[length] != '\0') {
+        length++;
+    }
+    printf("Length: %d\n", length);
+}
+
+int main() {
+    const char *str = "hi!";
+    mystrlen(str);
+    return 0;
+}
+