c语言程序设计课件ppt（英文）c program language 之6 points and array

Points and Array Xue Qing2009.4Terms the relationship between a,b,c ? If you declare int a1,a2,a3 as the students score , the number of the grades is large, representing and manipulating the data by means of unique identifiers will be cumbersome.How to group several data with the same type together ?ArrayThe same typeLimited numbersStore in sequenceOne dimensional Arrays 2 How to declare a array?Type array-name length All array members are the same typeAlso: size- How many array membersint a 10 3 How to access array members ?Name and subscriptFrom 0 to lenth-14 How to store array members in memory?a0a2a4a3a6a7a1a5a8a9memoryStore in sequence from the first element to the last one.a0a2a4a3a6a7a1a5a8a9memory5 How to initialize an array?int a10=1,2,3,4,5,6,7,8,9,0;float x5 = 1.9, 2.0 ;int a = 1, 2, 3, 4;main ( ) int i, int a10=1,2,3,4,5,6,7,8,9,10;for(i=0;i3 nothing change203 nothing change11 nothing change531 nothing change 121 nothing change651 nothing changeak=a0a0=minmain( ) int i , a10 , min ,k;for(i=0;iai ) /* find the smallest one */ min=ai ; k=i ; ak=a0; /* exchange the value */a0=min;for(i=0;i b j + 1 ) t = b j ; b j = b j + 1 ;b j + 1 = t ; Actual argument is array name Formal argument is array name One dimensional Arrays One dimensional Arrays Application : insert a new element in array Give numbers k, n , input k to the nth element in array , an=k 5 4 6 8 9 1 2 3 7int k,n , a10=5,4,6,8,9,1,2,3,7; scanf(“%d,%d”, 50, 4 5 4 6 8 50 9 1 2 3 7a4=50main( ) int k,n, i , a10=5,4,6,8,9,1,2,3,7; scanf(“%d,%d“,for(i=8; i=n; i-)ai+1=ai; /* move elements */an=k; /* insert new value */for(i=0;i=9;i+)printf(“%3d“,ai);One dimensional Arrays Application : delete an element from an array Give numbers n , delete the nth element in array 5 4 6 8 9 1 2 3 7 105 4 6 8 1 2 3 7 10 int k,n , a10=5,4,6,8,9,1,2,3,7,10; scanf(“%d”, 4 main( ) int a10=5,4,6,8,9,1,2,3,7,10;int n,i;scanf(“%d“,for(i=n;i=9;i+)ai=ai+1; /* move elements */for(i=0;i=9;i+)printf(“%3d“,ai);After moving the following element from n, ,the previrous value of an will be changedApplication : sort1 （气泡法）#define N 10main( ) /* 气泡法排序 ,大 小 */ int i,j,m,aN;for(i=0;iN;i+)scanf(“%d”,for(j=1;j=N-1;j+) /* N-1轮处理 */for(i=0;iN-j;i+) /* N-J次比较 */if(aiai+1) /* 顺序不对时交换 */ m=ai; ai=ai+1; ai+1=m;for(i=0;iN;i+)printf(“%5d”,ai); One dimensional Arrays Application : sort2（选择法）#define N 10main( ) /* 选择法排序 大 小 */ int i,j,m,p,aN;for(i=0;iN;i+) scanf(“%d”,for(j=0;jN-1;j+) /* N-1轮处理 */ p=j; /*p记录最大值的下标 */for(i=j+1;iN;i+) /*找第 J轮最大值下标 P*/if( apai ) p=i; m=ap;ap=aj;aj=m; /*ap,aj交换 */for(i=0;iN;i+)printf(“%5d”,ai); One dimensional Arrays Multi-dimensional Arrays How to describe some data like: C provides rectangular multi-dimensional arrays.Question 1 2 3 4 51 1 6 7 81 1 1 9 101 1 1 1 111 1 1 1 1How to define multi-dimensional array? How to store a multi-dimensional array in memory?How to initialize multi-dimensional array How to access members in multi-dimensional arrayMulti-dimensional Arrays Define a multi-dimensional array 1 2 34 5 67 8 9type array-name length1 length2 rows columnsint a33Array elements are stored row by row1 2 3 4 5 6 7 8 9The first row A 2D array is really a 1D array, each of whose elements itself is an array. How to initialize a multi-dimensional array int a23= 1,2,3 , 4,5,6 ; int a23=1,2,3,4,5,6； int a23=1,2,3; int a23=1,2,3; int a23=0,1,2,3;How to access members in multi-dimensional array?For int a 34, elements can be accessed by a i j , i from 0 to 2, j from 0 to 3Suppose 2D array a has m columns ， then access elements via : m * row + col + base_address , or the position of aij is : i*m+j+1 when a00 is the first one .Multi-dimensional Arrays Which one is correct: A) int a3 ; B) float a(3,4);C) double a14; D) float a(3)(4);If we have int a34, which is correct when access the elements:A) a 2 4 B) a 1,3 C) a 1+1 0 D) a (2)(1)a00 aiii*m+j+1Multi-dimensional Arrays Autogeneration a matrix without any input.1 2 3 4 51 1 6 7 81 1 1 9 101 1 1 1 111 1 1 1 1main ( ) int i,j,a55;k=2;for(i=0;i5;i+) /* loop in row */for(j=0;j5;j+) /* loop in column */if(j=i) aij=1; else aij=k+; for(i=0;i5;i+) for(j=0;j5;j+)printf(“%4d”,aij);printf(“n”); /* new line */ All values are 1 The value is increment one by one矩阵（乘法）main( ) /* 矩阵乘积 */ static int i,j,k， c22 ；static int a23=1,2,3,4,5,6, b32=2,1,0,4,3,2;for(i=0;i2;i+)for(j=0;j2;j+) cij=0; for(k=0;k=2;k+)cij= cij + aik*bkj; printf(“|%4d %4d|n”,c00,c01); printf(“|%4d %4d|n”,c10,c11);Multi-dimensional Arrays 矩阵（转置）main( ) /* 矩阵 转置 */ int i,j,k；static int a33=1,2,3,4,5,6， 7， 8， 9；for(i=0;i3;i+)for(j=0;ji;j+) /* 矩阵 转置 */ k=aij; aij= aji; aji=k; for(i=0;i3;i+) /*按行输出 */ for(j=0;j3;j+) printf(“%5d”,aij); printf(“n”);Multi-dimensional Arrays Pointers and Addresses int i = 3; float f = 10.0;double d = 1.0; char c =a;we define i. f. d. c as follows：1. Where are the variables stored?2. If we want to access a variable, is there another way except direct operation?C provides an operator and data type to solve above the problem -by pointer A pointer is a variable that contains the address of others A pointer is a group of cells (often two or four) that can hold an address100int k=100a=5 ; b=10 ; c=a+b; printf(“%d,%d,%d ”, a,b,c);main( ) int a , b , c, *pc ;a=5 ; b=10 ; pc=c=a+b; printf(“%d,%d,%d ”, a,b,*pc);A pointer can point to any variables or functions A pointer store others address when it point to it.VariableFunctionArraypointerAdvantages of using pointer:a) faster operation execution of program.b) fewer memory spaces.c) convenient operation, such as assignment, subtraction “-”,+,- and relational operation.Pointers and Addresses PointervariablePointerarrayarrayfunctionAint k ; int *pk; int a10 ; int *pa=a; int fun();int (*pf)()int *f() int *p3PointerPoints to an arrayint ( *p)5Pointers an