习题 2.9 //输入20个数分别找出其中最大的正整数、最小正整数、最大负正整数、最小负正整数

int main() {
    int num,i = 0,j = 0,k = 0;
    int maxpn,minpn,maxmn,minmn;
    scanf("%d",&num);
    if (num > 0) {
    j = 1;
    maxpn = num;
    minpn = num;
    }else if (num < 0){
    k = 1;
    maxmn = num;
    minmn = num;
    }
    while (i<19) {
        scanf("%d",&num);
        if (num<0) {
            if (k == 1){
            if (num > maxmn){
                maxmn = num;
            }else if (num < minmn){
                minmn = num;
            }
            }else {
             maxmn = num;
             minmn = num;
             k = 1;
            }

        }else if (num > 0) {
            if (j == 1){
            if (num > maxpn){
                maxpn = num;
            }else if(num < minpn) {
                minpn = num;
            }

        }else {
            maxpn = num;
            minpn = num;
            j = 1;
        }
        }
        i++;
    }
    printf("最大正整数是:%dn",maxpn);
    printf("最小正整数是:%dn",minpn);
    printf("最大负整数是:%dn",maxmn);
    printf("最小负整数是:%dn",minmn);
    return 0;
}