leetCode(55):Minimum Window Substring（limits.h頭文件）

Given a string S and a string T, find the minimum window in S which will contain all the characters in T in complexity O(n).

For example,
S = "ADOBECODEBANC"
T = "ABC"

Minimum window is "BANC".

Note:
If there is no such window in S that covers all characters in T, return the emtpy string "".

If there are multiple such windows, you are guaranteed that there will always be only one unique minimum window in S.

不會做，看了別人的程序，自己按他的思路寫了個。當作學學別人的編程技巧了。

class Solution {
public:
    string minWindow(string s, string t) {
        int slength=s.size();
    	int tlength=t.size();	
    	int alphArray[128];
    	fill_n(alphArray,128,-slength);
    	int minS,minL=INT_MAX;
    	for(int i=0;i<tlength;++i)
    		alphArray[t[i]]=alphArray[t[i]]>0?(++alphArray[t[i]]):1;
    	
    	int start=0;
    	for(int i=0,count=tlength;i<slength;++i)
    	{
    		if((--alphArray[s[i]]>=0) && (--count==0))
    		{
    			while(alphArray[s[start]]<=-slength || (++alphArray[s[start]]<=0))
    				++start;
    			if(minL>i-start+1)
    			{
    				minL=i-start+1;
    				minS=start;
    			}
    			count=1;//因爲丟棄了一個
    			++start;
    		}
    	}
    	return minL==INT_MAX?"":s.substr(minS,minL);
    }
};

以上程序中包括了兩個頭文件：<limits.h>、<algorithm>;前者定義了部分數據類型的極限取值（INT_MAX），後者是STL中相關算法（fill_n）

limits.h頭文件內容如下：

C語言的數據類型有四種：整形、浮點型、指針、聚合類型（數組、結構等），其中整形家族的變量包括：char, int, short, long, enum等。浮點數家族包括float, double等。

limits.h頭文件對整形家族變量範圍進行了宏定義。float.h定義了FLT_MAX, FLT_MIN, DBL_MAX, DBL_MIN。下面這張表搬運自維基百科。

 

Name	Description	Typical value		ANSI standard minimum- or maximum magnitude value
CHAR_BIT	Number of bits in a char	8		≥+8
SCHAR_MIN	Minimum value for a signed char	–128		≤–127
SCHAR_MAX	Maximum value for a signed char	+127		≥+127
UCHAR_MAX	Maximum value for an unsigned char	+255		≥+255
CHAR_MIN	Minimum value for a char	–128		≤–127 (if char is represented as a signed char; otherwise ≤0)
CHAR_MAX	Maximum value for a char	+127		≥+127 (if char is represented as a signed char; otherwise ≥+255)
MB_LEN_MAX	Maximum multi byte length of a character across all locales	varies, usually at least 4		≥+1
SHRT_MIN	Minimum value for a short int	–32,768		≤–32,767
SHRT_MAX	Maximum value for a short int	+32,767		≥+32,767
USHRT_MAX	Maximum value for an unsigned short int	+65,535		≥+65,535
INT_MIN	Minimum value for an int	–2,147,483,648		≤–32,767
INT_MAX	Maximum value for an int	+2,147,483,647		≥+32,767
UINT_MAX	Maximum value for an unsigned int	+4,294,967,295		≥+65,535
LONG_MIN	Minimum value for a long int	32 bit compiler	–2,147,483,648	≤–2,147,483,647
		64 bit compiler	–9,223,372,036,854,775,808
LONG_MAX	Maximum value for a long int	32 bit compiler	+2,147,483,647	≥+2,147,483,647
		64 bit compiler	+9,223,372,036,854,775,807
ULONG_MAX	Maximum value for an unsigned long int	32 bit compiler	+4,294,967,295	≥+4,294,967,295
		64 bit compiler	+18,446,744,073,709,551,615
LLONG_MIN	Minimum value for a long long int	–9,223,372,036,854,775,808		≤-9,223,372,036,854,775,807
LLONG_MAX	Maximum value for a long long int	+9,223,372,036,854,775,807		≥+9,223,372,036,854,775,807
ULLONG_MAX	Maximum value for an unsigned long long int	+18,446,744,073,709,551,615		≥+18,446,744,073,709,551,615