Use contains() in containers where possible.

diff --git a/verible/common/analysis/lint-rule-status.cc b/verible/common/analysis/lint-rule-status.cc
index eb36ab6..7a79a42 100644
--- a/verible/common/analysis/lint-rule-status.cc
+++ b/verible/common/analysis/lint-rule-status.cc

@@ -60,7 +60,7 @@
 bool AutoFix::AddEdits(const std::set<ReplacementEdit> &new_edits) {
   // Check for conflicts
   for (const auto &edit : new_edits) {
-    if (edits_.find(edit) != edits_.end()) {
+    if (edits_.contains(edit)) {
       return false;
     }
   }

diff --git a/verible/common/analysis/matcher/bound-symbol-manager.cc b/verible/common/analysis/matcher/bound-symbol-manager.cc
index 7c2030c..e34dce5 100644
--- a/verible/common/analysis/matcher/bound-symbol-manager.cc
+++ b/verible/common/analysis/matcher/bound-symbol-manager.cc

@@ -27,7 +27,7 @@
 namespace matcher {
 
 bool BoundSymbolManager::ContainsSymbol(const std::string &id) const {
-  return bound_symbols_.find(id) != bound_symbols_.end();
+  return bound_symbols_.contains(id);
 }
 
 const Symbol *BoundSymbolManager::FindSymbol(const std::string &id) const {

diff --git a/verible/verilog/analysis/checkers/forbidden-macro-rule.cc b/verible/verilog/analysis/checkers/forbidden-macro-rule.cc
index 34c3da1..3410e52 100644
--- a/verible/verilog/analysis/checkers/forbidden-macro-rule.cc
+++ b/verible/verilog/analysis/checkers/forbidden-macro-rule.cc

@@ -73,7 +73,7 @@
   if (MacroCallMatcher().Matches(symbol, &manager)) {
     if (const verible::SyntaxTreeLeaf *leaf = manager.GetAsLeaf("name")) {
       const auto &imm = InvalidMacrosMap();
-      if (imm.find(std::string(leaf->get().text())) != imm.end()) {
+      if (imm.contains(std::string(leaf->get().text()))) {
         violations_.insert(
             verible::LintViolation(leaf->get(), FormatReason(*leaf), context));
       }

diff --git a/verible/verilog/analysis/checkers/forbidden-symbol-rule.cc b/verible/verilog/analysis/checkers/forbidden-symbol-rule.cc
index 04558ea..4f832c1 100644
--- a/verible/verilog/analysis/checkers/forbidden-symbol-rule.cc
+++ b/verible/verilog/analysis/checkers/forbidden-symbol-rule.cc

@@ -81,7 +81,7 @@
   if (IdMatcher().Matches(symbol, &manager)) {
     if (const verible::SyntaxTreeLeaf *leaf = manager.GetAsLeaf("name")) {
       const auto &ism = InvalidSymbolsMap();
-      if (ism.find(std::string(leaf->get().text())) != ism.end()) {
+      if (ism.contains(std::string(leaf->get().text()))) {
         violations_.insert(
             verible::LintViolation(leaf->get(), FormatReason(*leaf), context));
       }

diff --git a/verible/verilog/analysis/checkers/struct-union-name-style-rule.cc b/verible/verilog/analysis/checkers/struct-union-name-style-rule.cc
index cd31f80..0217374 100644
--- a/verible/verilog/analysis/checkers/struct-union-name-style-rule.cc
+++ b/verible/verilog/analysis/checkers/struct-union-name-style-rule.cc

@@ -106,13 +106,13 @@
             "Section with unit names need to start with digit", context));
         return;
       }
-      if (exceptions_.find(std::string(ns)) != exceptions_.end()) {
+      if (exceptions_.contains(std::string(ns))) {
         continue;  // number + unit exception found
       }
       const auto &alpha =
           std::find_if(ns.begin(), ns.end(), absl::ascii_isalpha);
       const auto ns_substr = std::string(alpha, ns.end());
-      if (exceptions_.find(ns_substr) == exceptions_.end()) {
+      if (!exceptions_.contains(ns_substr)) {
         violations_.insert(
             LintViolation(*identifier_leaf,
                           "found digit followed by unit that is "

diff --git a/verible/verilog/analysis/checkers/void-cast-rule.cc b/verible/verilog/analysis/checkers/void-cast-rule.cc
index c9d9216..658d45a 100644
--- a/verible/verilog/analysis/checkers/void-cast-rule.cc
+++ b/verible/verilog/analysis/checkers/void-cast-rule.cc

@@ -98,7 +98,7 @@
   if (FunctionMatcher().Matches(symbol, &manager)) {
     if (const verible::SyntaxTreeLeaf *function_id = manager.GetAsLeaf("id")) {
       const auto &bfs = ForbiddenFunctionsSet();
-      if (bfs.find(std::string(function_id->get().text())) != bfs.end()) {
+      if (bfs.contains(std::string(function_id->get().text()))) {
         violations_.insert(LintViolation(function_id->get(),
                                          FormatReason(*function_id), context));
       }

diff --git a/verible/verilog/analysis/flow-tree.cc b/verible/verilog/analysis/flow-tree.cc
index c5e2c23..1f28aea 100644
--- a/verible/verilog/analysis/flow-tree.cc
+++ b/verible/verilog/analysis/flow-tree.cc

@@ -139,8 +139,7 @@
   }
   auto macro_iterator = conditional_iterator + 1;
   auto macro_identifier = macro_iterator->text();
-  if (conditional_macro_id_.find(macro_identifier) ==
-      conditional_macro_id_.end()) {
+  if (!conditional_macro_id_.contains(macro_identifier)) {
     conditional_macro_id_[macro_identifier] = conditional_macros_counter_;
     conditional_macros_.push_back(macro_iterator);
     conditional_macros_counter_++;

diff --git a/verible/verilog/analysis/verilog-linter-configuration.cc b/verible/verilog/analysis/verilog-linter-configuration.cc
index 4703127..42ed8f4 100644
--- a/verible/verilog/analysis/verilog-linter-configuration.cc
+++ b/verible/verilog/analysis/verilog-linter-configuration.cc

@@ -163,7 +163,7 @@
     // same configuration file, warn the user about it.
     // NOTE: ignore producing a warning if there is no configuration, just
     // disabing/enabling
-    if (!setting.configuration.empty() && rules.count(*rule_iter)) {
+    if (!setting.configuration.empty() && rules.contains(*rule_iter)) {
       absl::StrAppend(error, error->empty() ? "" : "\n", kRepeatedFlagMessage,
                       " \"", rule_name, "\" = ", setting.configuration);
       parsed_correctly = false;

diff --git a/verible/verilog/parser/verilog-lexical-context.cc b/verible/verilog/parser/verilog-lexical-context.cc
index 740e3fe..445dff7 100644
--- a/verible/verilog/parser/verilog-lexical-context.cc
+++ b/verible/verilog/parser/verilog-lexical-context.cc

@@ -46,7 +46,7 @@
        TK_endprogram, TK_endproperty, TK_endsequence, TK_endchecker,
        TK_endconnectrules, TK_enddiscipline, TK_endnature, TK_endparamset,
        TK_join, TK_join_any, TK_join_none});
-  return keywords->find(token_enum) != keywords->end();
+  return keywords->contains(token_enum);
 }
 
 void KeywordLabelStateMachine::UpdateState(int token_enum) {

diff --git a/verible/verilog/preprocessor/verilog-preprocess.cc b/verible/verilog/preprocessor/verilog-preprocess.cc
index 39e816a..89ddb7d 100644
--- a/verible/verilog/preprocessor/verilog-preprocess.cc
+++ b/verible/verilog/preprocessor/verilog-preprocess.cc

@@ -535,7 +535,7 @@
   const auto &macro_name = *macro_name_extract.value();
   const bool negative_if = (*ifpos)->token_enum() == PP_ifndef;
   const auto &defs = preprocess_data_.macro_definitions;
-  const bool name_is_defined = defs.find(macro_name->text()) != defs.end();
+  const bool name_is_defined = defs.contains(macro_name->text());
   const bool condition_met = (name_is_defined ^ negative_if);
 
   if ((*ifpos)->token_enum() == PP_elsif) {