- (void)addTarget:(id)target action:(SEL)action forControlEvents:(ASControlNodeEvent)controlEventMask
{
NSParameterAssert(action);
NSParameterAssert(controlEventMask != 0);
// Convert nil to [NSNull null] so that it can be used as a key for NSMapTable.
if (!target)
target = [NSNull null];
// Enumerate the events in the mask, adding the target-action pair for each control event included in controlEventMask
_ASEnumerateControlEventsIncludedInMaskWithBlock(controlEventMask, ^
(ASControlNodeEvent controlEvent)
{
// Do we already have an event table for this control event?
id<NSCopying> eventKey = _ASControlNodeEventKeyForControlEvent(controlEvent);
NSMapTable *eventDispatchTable = [_controlEventDispatchTable objectForKey:eventKey];
// Create it if necessary.
if (!eventDispatchTable)
{
// Create the dispatch table for this event.
eventDispatchTable = [NSMapTable weakToStrongObjectsMapTable];
[_controlEventDispatchTable setObject:eventDispatchTable forKey:eventKey];
}
// Have we seen this target before for this event?
NSMutableArray *targetActions = [eventDispatchTable objectForKey:target];
if (!targetActions)
{
// Nope. Create an actions array for it.
targetActions = [[NSMutableArray alloc] initWithCapacity:kASControlNodeActionDispatchTableInitialCapacity]; // enough to handle common types without re-hashing the dictionary when adding entries.
[eventDispatchTable setObject:targetActions forKey:target];
}
// Add the action message.
// Note that bizarrely enough UIControl (at least according to the docs) supports duplicate target-action pairs for a particular control event, so we replicate that behavior.
[targetActions addObject:NSStringFromSelector(action)];
});
self.userInteractionEnabled = YES;
}
下面这个方法是C 风格的方法，为什么要这么写呢？
12345678910
void _ASEnumerateControlEventsIncludedInMaskWithBlock(ASControlNodeEvent mask, void (^block)(ASControlNodeEvent anEvent))
{
// Start with our first event (touch down) and work our way up to the last event (touch cancel)
for (ASControlNodeEvent thisEvent = ASControlNodeEventTouchDown; thisEvent <= ASControlNodeEventTouchCancel; thisEvent <<= 1)
{
// If it's included in the mask, invoke the block.
if ((mask & thisEvent) == thisEvent)
block(thisEvent);
}
}
A peak element is an element that is greater than its neighbors.
Given an input array where num[i] ≠ num[i+1], find a peak element and return its index.
The array may contain multiple peaks, in that case return the index to any one of the peaks is fine.
You may imagine that num[-1] = num[n] = -∞.
For example, in array [1, 2, 3, 1], 3 is a peak element and your function should return the index number 2.
Implement regular expression matching with support for ‘.’ and ‘*’.
sequence is:
12345678910111213141516
'.' Matches any single character.
'*' Matches zero or more of the preceding element.
The matching should cover the entire input string (not partial).
The function prototype should be:
bool isMatch(const char *s, const char *p)
Some examples:
isMatch("aa","a") → false
isMatch("aa","aa") → true
isMatch("aaa","aa") → false
isMatch("aa", "a*") → true
isMatch("aa", ".*") → true
isMatch("ab", ".*") → true
isMatch("aab", "c*a*b") → true
The gray code is a binary numeral system where two successive values differ in only one bit.
Given a non-negative integer n representing the total number of bits in the code, print the sequence of gray code. A gray code sequence must begin with 0.
For example, given n = 2, return [0,1,3,2]. Its gray code sequence is:
1234
00 - 0
01 - 1
11 - 3
10 - 2
Note:
For a given n, a gray code sequence is not uniquely defined.
For example, [0,2,3,1] is also a valid gray code sequence according to the above definition.
For now, the judge is able to judge based on one instance of gray code sequence. Sorry about that.
Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target.
Note:
Elements in a quadruplet (a,b,c,d) must be in non-descending order. (ie, a ≤ b ≤ c ≤ d)
The solution set must not contain duplicate quadruplets.
For example, given array S = {1 0 -1 0 -2 2}, and target = 0.
A solution set is:
classSolution{public:vector<vector<int>>fourSum(vector<int>&num,inttarget){// Note: The Solution object is instantiated only once and is reused by each test case.vector<int>tmp;vector<vector<int>>res;if(num.empty())returnres;sort(num.begin(),num.end());for(inti=0;i<num.size();i++){intcur=target-num[i];for(intj=i+1;j<num.size();j++){inttemp=cur-num[j];intstart=j+1,end=num.size()-1;while(start<end){if(num[start]+num[end]==temp){tmp.push_back(num[i]);tmp.push_back(num[j]);tmp.push_back(num[start]);tmp.push_back(num[end]);res.push_back(tmp);tmp.clear();start++;end--;while(start<end&&num[start]==num[start-1])start++;while(start<end&&num[end]==num[end+1])end--;}elseif(num[start]+num[end]<temp){start++;while(start<end&&num[start]==num[start-1])start++;}else{end--;while(start<end&&num[end]==num[end+1])end--;}}while(j<num.size()&&num[j]==num[j+1])j++;}while(i<num.size()&&num[i]==num[i+1])i++;}returnres;}};