refactor less likely to overflow

Cargo.toml

@@ -4,3 +4,4 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
+num = "0.4.3"

src/algorithm.rs

@@ -0,0 +1,41 @@
+use num::traits::{FromPrimitive, Num};
+
+pub fn binary_search_threshold<T, F>(mut ok: T, mut ng: T, mut check: F, threshold: T) -> T
+where
+    T: Num + PartialOrd + FromPrimitive + Copy,
+    F: FnMut(T) -> bool,
+{
+    while if ok > ng { ok - ng } else { ng - ok } > threshold {
+        let mid = if ok > ng {
+            ng + (ok - ng) / T::from_usize(2).unwrap()
+        } else {
+            ok + (ng - ok) / T::from_usize(2).unwrap()
+        };
+        if check(mid) {
+            ok = mid;
+        } else {
+            ng = mid;
+        }
+    }
+    ok
+}
+
+pub fn binary_search_trial<T, F>(mut ok: T, mut ng: T, mut check: F, trial: usize) -> T
+where
+    T: Num + PartialOrd + FromPrimitive + Copy,
+    F: FnMut(T) -> bool,
+{
+    for _ in 0..trial {
+        let mid = if ok > ng {
+            ng + (ok - ng) / T::from_usize(2).unwrap()
+        } else {
+            ok + (ng - ok) / T::from_usize(2).unwrap()
+        };
+        if check(mid) {
+            ok = mid;
+        } else {
+            ng = mid;
+        }
+    }
+    ok
+}

src/lib.rs

@@ -1 +1,2 @@
 pub mod graph;
+pub mod algorithm;