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+/*
+Challenge 209
+
+Task 1: Special Bit Characters
+Submitted by: Mohammad S Anwar
+
+You are given an array of binary bits that ends with 0.
+
+Valid sequences in the bit string are:
+
+[0] -decodes-to-> "a"
+[1, 0] -> "b"
+[1, 1] -> "c"
+
+Write a script to print 1 if the last character is an “a” otherwise print 0.
+Example 1
+
+Input: @bits = (1, 0, 0)
+Output: 1
+
+The given array bits can be decoded as 2-bits character (10) followed by
+1-bit character (0).
+
+Example 2
+
+Input: @bits = (1, 1, 1, 0)
+Output: 0
+
+Possible decode can be 2-bits character (11) followed by 2-bits character
+(10) i.e. the last character is not 1-bit character.
+*/
+
+#include <iostream>
+#include <string>
+
+std::string decode(const std::string& in) {
+    std::string out;
+    const char* p = in.c_str();
+    while (*p) {
+        switch (*p) {
+        case '0': out.push_back('a'); p++; break;
+        case '1':
+            p++;
+            switch (*p) {
+            case '0': out.push_back('b'); p++; break;
+            case '1': out.push_back('c'); p++; break;
+            default: std::cerr << "invalid input" << std::endl; exit(EXIT_FAILURE);
+            }
+            break;
+        default: std::cerr << "invalid input" << std::endl; exit(EXIT_FAILURE);
+        }
+    }
+    return out;
+}
+
+int main(int argc, char* argv[]) {
+    argv++; argc--;
+    if (argc != 1) {
+        std::cerr << "usage: ch-2 str" << std::endl;
+        return EXIT_FAILURE;
+    }
+
+    std::string out = decode(argv[0]);
+    int result = (!out.empty() && out.back()=='a') ? 1 : 0;
+    std::cout << result << std::endl;
+}