intmain(){int i =0;int count =0;for(i =1; i <=100; i++){if(i %10==9)//打印個位含9的個數{
count++;}if(i /10==9)//打印十位含9的個數{
count++;}}printf("count = %d\n",count);return0;}
打印1/1-1/2+1/3-1/4+…+1/99-1/100的結果
intmain(){int i =0;double sum =0.0;//結果含小數,定義爲浮點數int flag =1;for(i =1; i <=100; i++){
sum += flag*(1.0/ i);//"/"左右兩邊有一個浮點數,結果即爲浮點數
flag =-flag;}printf("sum = %lf\n",sum);return0;}
求一個數列十個元素的最大值
intmain(){int i =0;int arr[10]={0};int max =0;for(i =0; i <10; i++){scanf("%d",&arr[i]);}
max = arr[0];for(i =0; i <10; i++){if(max < arr[i]){
max = arr[i];}}printf("最大數max = %d\n",max);return0;}
在一個有序數組中查找具體某個數字n
intmain(){int arr[10]={1,2,3,4,5,6,7,8,9,10};int i =0;int k =7;//k爲要查找的數字for(i =0; i <10; i++){if(arr[i]== k){printf("找到了,下標爲:%d\n",i);}}if(i >=10){printf("找不到,該數組沒有需查找的數\n");}return0;}//我們可以發現上述查找方式,一個一個查找,效率比較低//下面介紹另一種方式,折半查找法(僅限於有序數列使用)intmain(){int arr[10]={1,2,3,4,5,6,7,8,9,10};int k =7;int left =0;int right =(sizeof(arr)/sizeof(arr[0]))-1;while(left <= right){int mid =(left + right)/2;if(arr[mid]<= k){
left = mid +1;}if(arr[mid]>= k){
right = mid -1;}if(arr[mid]== k){printf("找到了,下標爲:%d\n",mid);}}printf("找不到\n");return0;}