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在一个有序数组中通过二分查找法来找出具体某个数字

1.直接用二分法查找

#includeint main(){int arr[] = { 1,2,3,4,5,6,7,8,9,10 };//建立一个有序的数组int k;scanf("%d", &k);//输入你要查找的数int left = 0;int sz = sizeof(arr) / sizeof(arr[0]);//计算数组的长度int right = sz - 1;while (left <= right){int mid = (left + right) / 2;if (arr[mid] > k){right = mid - 1;}else if (arr[mid] < k){left = mid + 1;}else{printf("找到了下标是%d", mid);break;}}if (left > right)printf("找不到了\n");return 0;}

2.写一个函数来表达二分查找法

#includeint binary_search(int arr[], int k, int sz){int left = 0;int right = sz - 1;while (left <= right){int mid = (left + right) / 2;if (arr[mid] > k){right = mid - 1;}else if (arr[mid] < k)left = mid + 1;else{return mid;}}return -1;}int main(){int arr[] = { 1,2,3,4,5,6,7,8,9,10 };int k;scanf("%d", &k);int sz = sizeof(arr) / sizeof(arr[0]);int ret=binary_search(arr, k, sz);if (ret == -1)printf("没找到\n");elseprintf("找到了,下标是%d\n", ret);return 0;}

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