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

---