一些简单算法

1、打印0-100之间的素数

  for (int i =0;i<100;i++){
    int r = [self isPrime:i];
    if(r==1){
        NSLog(@"%d",i);
    }
}

-(int)isPrime:(int)number{
    for(int i=0;i<=sqrt(number);i++){
      if(number%i==0)  return0;  
    }
    return 1;
}

2、求两个整数的最大公约数

int gcd(int a,int b){
    int temp = 0;
    if(a<b){
        temp = a;
        a = b;
        b = temp;
    }

    while (b!=0) {
        temp = a % b;
        a = b;
        b = temp;
        NSLog(@"a:%d b:%d",a,b);
    }
    return a;
}

3、给定一个字符串，输出本字符串中只出现一次并且最靠前的那个字符的位置？如“abaccddeeef”,字符是b,输出应该是2

int main(int argc, const char * argv[]) {
    char *inputStr = "abacddbeeef";
    char *outputStr = strOutPut(inputStr);
    NSLog(@"%c",*outputStr);
}

char *strOutPut(char *s){
    char str[100];
    char *p = s;
    int  index = 0;
    while (*s != '\0') {
        if(compareDifferentChar(*s, p)==1){
            str[index] = *s;
            index++;
        }
        s++;
    }
    return &str;
}

int compareDifferentChar(char c,char *s){
    int i = 0;
    while (*s != '\0' && i<=1) {
        if (*s == c) {
            i++;
        }
        s++;
    }
    if (i == 1) {
        return 1;
    }else{
        return 0;
    }
}