iOS－－难倒一大片的问题

//

//  main.m   

//  10.27＊＊＊＊＊

//

//  Created by  on 15/10/27.

//  Copyright (c) 2015年 . All rights reserved.

//

 

#import <Foundation/Foundation.h>

#import "Student.h"

#import "Teacher.h"

 

int main(int argc, const char * argv[]) {

    @autoreleasepool {

        

        Teacher *jieyang=[[Teacher alloc]init];

        jieyang.age=25;

        jieyang.grade=@"高级";

        NSMutableArray *name=[NSMutableArray arrayWithObjects:@"赵三",@"钱三",@"孙三",@"李三",@"周三",@"吴三",@"郑三",@"王三",@"张宇",@"李荣生", nil];

        NSMutableArray *score=[NSMutableArray arrayWithObjects:@"85",@"69",@"97",@"84",@"57",@"88",@"99",@"87",@"100",@"100",nil];

        

//        NSDictionary *st=@{name[0]:score[0],name[1]:score[1],name[2]:score[2],name[3]:score[3],name[4]:score[4],name[5]:score[5],name[6]:score[6],name[7]:score[7],name[8]:score[8],name[9]:score[9]};

        

        int a=(int)score.count;

        for (int j=0; j<a+7; j++) {                               //为什么a+7？

            for (int i=0; i<a-i+7; i++) {                        //为什么a-i+7？

／／如果改为a－1的话就排不完了

                float a=[score[i] floatValue];

                float b=[score[i+1] floatValue];

                if (a<b) {

                    [score exchangeObjectAtIndex:i withObjectAtIndex:(i+1)];

                    [name exchangeObjectAtIndex:i withObjectAtIndex:(i+1)];

                }

            }

        }

        for (int i=0; i<score.count; i++) {

            NSArray *arr1=name[i];

            NSArray *arr=score[i];

            NSLog(@"%@的成绩是：%@",arr1,arr);

        }

        float total = 0.0;

        for (NSString *s in score) {

            float a=[s floatValue];

            total=a+total;

        }

        float avy=total/10;

        NSLog(@"xx老师班学生的平均成绩为%f",avy);

        NSString *grad;

        if (avy>=90) {

            grad=@"高级讲师";

            NSLog(@"xx老师现在等级为%@",grad);

        }else if (avy>=80){

            grad=@"中级讲师";

            NSLog(@"xx老师现在等级为%@",grad);

        }else if (avy>=75){

            grad=@"低级讲师";

            NSLog(@"xx老师现在等级为%@",grad);

        }else if (avy<75){

            grad=@"实习讲师";

            NSLog(@"xx老师现在等级为%@",grad);

        }

    }

    return 0;

}

---

//

//  Teacher.h

//  10.27＊＊＊＊＊

//

//  Created by  on 15/10/27.

//  Copyright (c) 2015年 . All rights reserved.

//

#import <Foundation/Foundation.h>

#import "Student.h"

@interface Teacher : NSObject

@property (nonatomic,assign) int       age;

@property (nonatomic,strong) NSString *grade;

@end

---

//

//  Teacher.m

//  10.27＊＊＊＊＊

//

//  Created by  on 15/10/27.

//  Copyright (c) 2015年 . All rights reserved.

//

#import "Teacher.h"

@implementation Teacher 

@end

---

//

//  Student.h

//  10.27＊＊＊＊＊

//

//  Created by  on 15/10/27.

//  Copyright (c) 2015年 . All rights reserved.

//

#import <Foundation/Foundation.h>

@interface Student : NSObject

@property (nonatomic,strong) NSString *name;

@property (nonatomic,assign) float    score;

@end

---

---

//

//  Student.m

//  10.27＊＊＊＊＊

//

//  Created by  on 15/10/27.

//  Copyright (c) 2015年 . All rights reserved.

//

#import "Student.h"

@implementation Student

@end

---