fix north_east_lattice_paths.hpp

hitonanode · hitonanode · commit 3e0a3628acb3 · 2026-01-18T14:26:12.000+09:00
diff --git a/other_algorithms/north_east_lattice_paths.hpp b/other_algorithms/north_east_lattice_paths.hpp
@@ -171,6 +171,7 @@ NorthEastLatticePathsBothBounded(const std::vector<int> &lb, const std::vector<i
     for (int i = 1; i < n; ++i) {
         assert(lb[i - 1] <= lb[i]);
         assert(ub[i - 1] <= ub[i]);
+        if (ub[i - 1] <= lb[i]) return std::vector<MODINT>(ub.back() - lb.back());
     }
 
     for (int i = 0; i < n; ++i) {

Original file line number	Diff line number	Diff line change
`@@ -171,6 +171,7 @@ NorthEastLatticePathsBothBounded(const std::vector<int> &lb, const std::vector<i`
`171`	`171`	`for (int i = 1; i < n; ++i) {`
`172`	`172`	`assert(lb[i - 1] <= lb[i]);`
`173`	`173`	`assert(ub[i - 1] <= ub[i]);`
	`174`	`+ if (ub[i - 1] <= lb[i]) return std::vector<MODINT>(ub.back() - lb.back());`
`174`	`175`	`}`
`175`	`176`
`176`	`177`	`for (int i = 0; i < n; ++i) {`