048

048/main.rs

@@ -0,0 +1,26 @@
+// https://rob.co.bb/posts/2019-02-10-modular-exponentiation-in-rust/
+fn mod_pow(mut base: u128, mut exp: u128, modulus: u128) -> u128 {
+    if modulus == 1 { return 0 }
+    let mut result = 1;
+    base = base % modulus;
+    while exp > 0 {
+        if exp % 2 == 1 {
+            result = result * base % modulus;
+        }
+        exp = exp >> 1;
+        base = base * base % modulus
+    }
+    result
+}
+
+
+fn main() {
+    let m = 10000000000;
+    let mut res = 0u128;
+    for n in 1..1000 {
+        let t = mod_pow(n, n, m);
+        res += t;
+        res = res % m;
+    }
+    println!("{}", res);
+}