update interface of ST walk to be more useful

Author: lrvideckis

library/data_structures_[l,r]/seg_tree_uncommon/max_right.hpp

@@ -1,9 +1,10 @@
-int max_right(int l, int r, const auto& f) {
-  if (T x = s[l + n]; f(x))
+void max_right(int l, int r, const auto& f) {
+  if (T x = s[l + n]; f(x, l))
     for (l++; l <= r;) {
-      int u = l + n, v = __lg(min(u & -u, r - l + 1));
-      if (T y = op(x, s[u >> v]); f(y)) l += 1 << v, x = y;
-      else r = l + (1 << v) - 2;
+      int u = l + n, v = __lg(min(u & -u, r - l + 1)),
+          m = l + (1 << v) - 1;
+      if (T y = op(x, s[u >> v]); f(y, m))
+        l = m + 1, x = y;
+      else r = m - 1;
     }
-  return l;
 }

library/data_structures_[l,r]/seg_tree_uncommon/min_left.hpp

@@ -1,10 +1,11 @@
 int min_left(int l, int r, const auto& f) {
-  if (T x = s[r + n]; f(x))
+  if (T x = s[r + n]; f(x, r))
     for (r--; l <= r;) {
-      int u = r + 1 + n, v = __lg(min(u & -u, r - l + 1));
-      if (T y = op(s[(u - 1) >> v], x); f(y))
-        r -= 1 << v, x = y;
-      else l = r - (1 << v) + 2;
+      int u = r + 1 + n, v = __lg(min(u & -u, r - l + 1)),
+          m = r - (1 << v) + 1;
+      if (T y = op(s[(u - 1) >> v], x); f(y, m))
+        r = m - 1, x = y;
+      else l = m + 1;
     }
   return r;
 }

tests/library_checker_aizu_tests/data_structures/simple_tree_inc_line.test.cpp

@@ -30,39 +30,51 @@ int main() {
       array<int, 2> res = st.query(l, r);
       {
         array<int, 2> walk_res = {1, 0};
-        int idx = st.max_right(l, r,
-          [&](const array<int, 2>& curr_line) -> bool {
+        int idx = -1;
+        st.max_right(l, r,
+          [&](const array<int, 2>& curr_line,
+            int m) -> bool {
+            idx = m;
             walk_res = curr_line;
             return 1;
           });
         assert(res == walk_res);
-        assert(idx == r + 1);
+        assert(idx == r);
       }
       {
         array<int, 2> walk_res = unit;
-        int idx = st.max_right(l, r,
-          [&](const array<int, 2>& curr_line) -> bool {
+        int idx = -1;
+        st.max_right(l, r,
+          [&](const array<int, 2>& curr_line,
+            int m) -> bool {
             walk_res = curr_line;
+            idx = m;
             return 0;
           });
         assert(walk_res == st.query(l, l));
         assert(idx == l);
       }
       {
         array<int, 2> walk_res = unit;
-        int idx = st.min_left(l, r,
-          [&](const array<int, 2>& curr_line) -> bool {
+        int idx = -1;
+        st.min_left(l, r,
+          [&](const array<int, 2>& curr_line,
+            int m) -> bool {
             walk_res = curr_line;
+            idx = m;
             return 1;
           });
         assert(walk_res == res);
-        assert(idx == l - 1);
+        assert(idx == l);
       }
       {
         array<int, 2> walk_res = unit;
-        int idx = st.min_left(l, r,
-          [&](const array<int, 2>& curr_line) -> bool {
+        int idx = -1;
+        st.min_left(l, r,
+          [&](const array<int, 2>& curr_line,
+            int m) -> bool {
             walk_res = curr_line;
+            idx = m;
             return 0;
           });
         assert(walk_res == st.query(r, r));

tests/library_checker_aizu_tests/data_structures/simple_tree_inc_walk.test.cpp

@@ -22,14 +22,20 @@ int main() {
       cout << st.query(k, k) << '\n';
     } else if (type == 3) {
       // returns first element in [k,n-1] such that mx > 0
-      int idx = st.max_right(k, n - 1,
-        [&](int mx) { return mx == 0; });
-      if (idx == n) idx = -1;
+      int idx = -1;
+      st.max_right(k, n - 1, [&](int mx, int m) {
+        if (mx == 0) return 1;
+        idx = m;
+        return 0;
+      });
       cout << idx << '\n';
     } else {
       assert(type == 4);
-      cout << st.min_left(0, k, [&](int mx) {
-        return mx == 0;
+      int idx = -1;
+      cout << st.min_left(0, k, [&](int mx, int m) {
+        if (mx == 0) return 1;
+        idx = m;
+        return 0;
       }) << '\n';
     }
   }