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Task/Longest-increasing-subsequence/Objective-C/longest-increasing-subsequence.m

@@ -0,0 +1,53 @@
+#import <Foundation/Foundation.h>
+
+@interface Node : NSObject {
+@public
+  id val;
+  Node *back;
+}
+@end
+
+@implementation Node
+@end
+
+@interface NSArray (LIS)
+- (NSArray *)longestIncreasingSubsequenceWithComparator:(NSComparator)comparator;
+@end
+
+@implementation NSArray (LIS)
+- (NSArray *)longestIncreasingSubsequenceWithComparator:(NSComparator)comparator {
+  NSMutableArray *pileTops = [[NSMutableArray alloc] init];
+  // sort into piles
+  for (id x in self) {
+    Node *node = [[Node alloc] init];
+    node->val = x;
+    int i = [pileTops indexOfObject:node
+                      inSortedRange:NSMakeRange(0, [pileTops count])
+                            options:NSBinarySearchingInsertionIndex|NSBinarySearchingFirstEqual
+                    usingComparator:^NSComparisonResult(Node *node1, Node *node2) {
+                      return comparator(node1->val, node2->val);
+                    }];
+    if (i != 0)
+      node->back = pileTops[i-1];
+    pileTops[i] = node;
+  }
+
+  // follow pointers from last node
+  NSMutableArray *result = [[NSMutableArray alloc] init];
+  for (Node *node = [pileTops lastObject]; node; node = node->back)
+    [result addObject:node->val];
+  return [[result reverseObjectEnumerator] allObjects];
+}
+@end
+
+int main(int argc, const char *argv[]) {
+  @autoreleasepool {
+    for (NSArray *d in @[@[@3, @2, @6, @4, @5, @1],
+         @[@0, @8, @4, @12, @2, @10, @6, @14, @1, @9, @5, @13, @3, @11, @7, @15]])
+      NSLog(@"an L.I.S. of %@ is %@", d,
+            [d longestIncreasingSubsequenceWithComparator:^NSComparisonResult(id obj1, id obj2) {
+        return [obj1 compare:obj2];
+      }]);
+  }
+  return 0;
+}