Validate CAS numbers

.vscode/settings.json

@@ -0,0 +1,3 @@
+{
+    "cmake.configureOnOpen": true
+}

.vscode/tasks.json

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+{
+    "tasks": [
+        {
+            "type": "cppbuild",
+            "label": "C/C++: gcc build active file",
+            "command": "/usr/bin/gcc",
+            "args": [
+                "-fdiagnostics-color=always",
+                "-g",
+                "${file}",
+                "-o",
+                "${fileDirname}/${fileBasenameNoExtension}"
+            ],
+            "options": {
+                "cwd": "${fileDirname}"
+            },
+            "problemMatcher": [
+                "$gcc"
+            ],
+            "group": {
+                "kind": "build",
+                "isDefault": true
+            },
+            "detail": "Task generated by Debugger."
+        }
+    ],
+    "version": "2.0.0"
+}

cas.c

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+// Program to validate if a CAS number is valid using its last check digit
+// CAS number is formatted as XXXXXXX-XX-X where the first part is 2-7 digits, the second part is 2 digits, and the last part is 1 check digit
+// Can be represented as Ni ... N4 N3 - N2 N1 - R where R is the check digit
+// The check digit is calculated by multiplying each digit by its position and summing them up, then taking the remainder of the sum divided by 10
+// https://www.cas.org/support/documentation/chemical-substances/checkdig
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+
+#define MIN_CAS_LENGTH 7
+#define MAX_CAS_LENGTH 12
+
+int validateCas(char *casNumber);
+
+int main()
+{
+
+    printf("Enter a CAS number: ");
+    char casNumber[15] = {0};
+    scanf("%s", casNumber);
+
+    printf("The CAS number is: %s\nCheck-digit: %d\n", casNumber, casNumber[strlen(casNumber) - 1] - '0');
+
+    switch (validateCas(casNumber))
+    {
+    case -1:
+        printf("Invalid CAS number\n");
+        break;
+    case 0:
+        printf("Invalid CAS number (check digit mismatch)\n");
+        break;
+    case 1:
+        printf("Valid CAS number\n");
+        break;
+    }
+
+    return EXIT_SUCCESS;
+}
+
+int validateCas(char *casNumber)
+{
+    int casLen = strlen(casNumber);
+    int checkdigit = casNumber[casLen - 1] - '0';
+    if (
+        casNumber[casLen - 2] != '-' || casNumber[casLen - 5] != '-' ||
+        casLen < MIN_CAS_LENGTH || casLen > MAX_CAS_LENGTH ||
+        checkdigit < 0 || checkdigit > 9
+    )
+    {
+        return -1;
+    }
+
+    char strippedCas[15] = {0};
+    int j = 0;
+    for (int i = 0; i < casLen - 2; i++)
+    {
+        if (casNumber[i] != '-' && !isdigit(casNumber[i]))
+        {
+            return -1;
+        }
+        if (casNumber[i] != '-')
+        {
+            strippedCas[j] = casNumber[i];
+            j++;
+        }
+    }
+    strippedCas[j] = '\0';
+    printf("Stripped CAS number: %s\n", strippedCas);
+    int sum = 0;
+    for (int i = 0; i < strlen(strippedCas); i++)
+    {
+        sum += (strippedCas[i] - '0') * (strlen(strippedCas) - i);
+    }
+    printf("Sum: %d\n", sum);
+
+    return sum % 10 == checkdigit;
+}

zig-cache/o/74c27f1902f95e35c91bb05395a1a801/dependencies.zig

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+pub const imports = struct {
+};
+pub const build_root = struct {
+};