几个经典的小算法

1. 最大子序列和问题

 1 int MaxSubsquenceSum(const int A[],int N){
 2 
 3    int ThisSum,MaxSum,j;
 4 
 5    ThisSum = MaxSum = 0;
 6 
 7    for(j=0;j<N;j++){
 8 
 9       ThisSum += A[j];
10 
11       if(ThisSum > MaxSum)
12 
13           MaxSum = ThisSum;
14 
15       else if(ThisSum < 0)
16 
17           ThisSum = 0;
18 
19    }
20 
21    return MaxSum;
22 
23 }

2. 二分查找法

 1 int BinarySearch(const ElementType A[], ElementType X, int N){
 2 
 3    int Low,Mid,High;
 4 
 5    Low=0;High=N-1;
 6 
 7    while(Low <= High){
 8 
 9       Mid = (Low + High)/2;
10 
11       if(a[Mid] < X)
12 
13          Low = Mid + 1;
14 
15       else if(a[Mid] > X)
16 
17          High = Mid -1;
18 
19       else
20 
21          return Mid;
22 
23    }
24 
25    return NotFound;
26 
27 }

3.欧几里德算法（求最大公因数）

 1 unsigned int Gcd(unsigned int M,unsigned int N){
 2 
 3    unsigned int Rem;
 4 
 5    while(N > 0){
 6 
 7       Rem = M % N;
 8 
 9       M = N;
10 
11       N = Rem;
12 
13    }
14 
15    return M;
16 
17 }

4.幂运算（计算X的n次方）

 1 long int Pow(long int X,unsigned int N){
 2 
 3    if(N == 0) return 1;
 4 
 5    if(N == 1) return X;
 6 
 7    if(IsEven(N)) return Pow(X * X,N/2);
 8 
 9    else return Pow(X * X,N/2) * X;
10 
11 }