add permutation.rs for 51 (WIP)

euler51/src/permutation.rs

@@ -0,0 +1,75 @@
+struct PositionPermut {
+    max_length: usize,
+    number_of_digits: usize,
+    idx: usize,
+    total_number_of_iterations: usize,
+}
+
+impl Iterator for PositionPermut {
+    type Item = Vec<i64>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.idx == (self.total_number_of_iterations) {
+            return None;
+        };
+        let pos1 = self.idx % self.number_of_digits;
+        let pos0 = 0;
+        let x = vec![pos0 as i64, pos1 as i64];
+        let result = Some(x);
+        self.idx += 1;
+        result
+    }
+}
+
+impl PositionPermut {
+    fn new(max_length: usize) -> Self {
+        assert!(max_length >= 3);
+        let total_number_of_iterations = (1..max_length + 1).sum();
+        Self {
+            max_length,
+            number_of_digits: 2,
+            idx: 0,
+            total_number_of_iterations,
+        }
+    }
+    fn test(&mut self) {
+        // length_of_numbers = 4
+        // number_of_digits = 2
+        [0, 1];
+        [0, 2];
+        [0, 3];
+        [1, 2];
+        [1, 3];
+        [2, 3];
+        // number_of_digits = 3
+        [0, 1, 2];
+        [0, 1, 3];
+        [0, 2, 3];
+        [1, 2, 3];
+    }
+}
+
+#[cfg(test)]
+mod test {
+    #[test]
+    fn test_permutation() {
+        use crate::permutation::PositionPermut;
+        use std::collections::HashSet;
+
+        let permutator = PositionPermut::new(3);
+        let result: HashSet<_> = permutator.into_iter().collect();
+        let mut solution = HashSet::new();
+        solution.insert(vec![0, 1]);
+        solution.insert(vec![0, 2]);
+        solution.insert(vec![0, 3]);
+        solution.insert(vec![1, 2]);
+        solution.insert(vec![1, 3]);
+        solution.insert(vec![2, 3]);
+        // solution.insert(vec![0, 1, 2]);
+        // solution.insert(vec![0, 1, 3]);
+        // solution.insert(vec![0, 2, 3]);
+        // solution.insert(vec![1, 2, 3]);
+        // assert_eq!(result.len(), solution.len());
+        assert_eq!(result, solution);
+    }
+}