Use std::adjacent_find instead of std::unique

When detecting duplicates, it is more efficient to use std::adjacent_find
than it is to use std::unique.

Change-Id: Ib6b4671c10848bb7dd10aa7a1baeffc8c9c825b5

internal/ceres/local_parameterization.cc

diff --git a/internal/ceres/local_parameterization.cc b/internal/ceres/local_parameterization.cc
index 8200476..9e05cba 100644
--- a/internal/ceres/local_parameterization.cc
+++ b/internal/ceres/local_parameterization.cc
@@ -30,6 +30,7 @@
 
 #include "ceres/local_parameterization.h"
 
+#include <algorithm>
 #include "ceres/householder_vector.h"
 #include "ceres/internal/eigen.h"
 #include "ceres/internal/fixed_array.h"
@@ -98,7 +99,7 @@
 
   vector<int> constant = constant_parameters;
   sort(constant.begin(), constant.end());
-  CHECK(unique(constant.begin(), constant.end()) == constant.end())
+  CHECK(std::adjacent_find(constant.begin(), constant.end()) == constant.end())
       << "The set of constant parameters cannot contain duplicates";
   CHECK_LT(constant_parameters.size(), size)
       << "Number of parameters held constant should be less "

internal/ceres/problem_impl.cc

diff --git a/internal/ceres/problem_impl.cc b/internal/ceres/problem_impl.cc
index 8547d5d..bb952be 100644
--- a/internal/ceres/problem_impl.cc
+++ b/internal/ceres/problem_impl.cc
@@ -249,10 +249,11 @@
     // Check for duplicate parameter blocks.
     vector<double*> sorted_parameter_blocks(parameter_blocks);
     sort(sorted_parameter_blocks.begin(), sorted_parameter_blocks.end());
-    vector<double*>::const_iterator duplicate_items =
-        unique(sorted_parameter_blocks.begin(),
-               sorted_parameter_blocks.end());
-    if (duplicate_items != sorted_parameter_blocks.end()) {
+    const bool has_duplicate_items =
+        (std::adjacent_find(sorted_parameter_blocks.begin(),
+                            sorted_parameter_blocks.end())
+         != sorted_parameter_blocks.end());
+    if has_duplicate_items {
       string blocks;
       for (int i = 0; i < parameter_blocks.size(); ++i) {
         blocks += StringPrintf(" %p ", parameter_blocks[i]);