二分查找问题全集..doc

二分查找问题全集 1，原始二分查找 题目：给定一个有序（非降序）数组A，求任意一个i使得A[i]等于target，不存在则返回-1 例如：[2,4,6,8,9]找(4) 位置1 1.1 递归版 [cpp] view plain copy print? int?bSearch(int?a[],?int?low,?int?high,?int?target){?? ????if(low??high)?? ????????return?-1;?? ????int?mid?=?(low?+?high)/2;?? ????if(targeta[mid])?? ????????return?bSearch(a,low,mid-1,target);?? ????else?if(targeta[mid])?? ????????return?bSearch(a,mid+1,high,target);?? ????//if(target?==?a[mid])?? ????return?mid;?? }?? int bSearch(int a[], int low, int high, int target){ if(low high) return -1; int mid = (low + high)/2; if(targeta[mid]) return bSearch(a,low,mid-1,target); else if(targeta[mid]) return bSearch(a,mid+1,high,target); //if(target == a[mid]) return mid; } 1.2 迭代版 [cpp] view plain copy print? int?search(int?A[],?int?n,?int?target)?? {?? ????int?low?=?0,?high?=?n-1;?? ????while(low?=?high)?? ????{?? ????????//?注意：若使用(low+high)/2求中间位置容易溢出?? ????????int?mid?=?low+((high-low)1);??? ????????if(A[mid]?==?target)?? ????????????return?mid;?? ????????else?if(A[mid]??target)?? ????????????low?=?mid+1;?? ????????else?//?A[mid]??target?? ????????????high?=?mid-1;?? ????}?? ????return?-1;?? }?? int search(int A[], int n, int target) { int low = 0, high = n-1; while(low = high) { // 注意：若使用(low+high)/2求中间位置容易溢出 int mid = low+((high-low)1); if(A[mid] == target) return mid; else if(A[mid] target) low = mid+1; else // A[mid] target high = mid-1; } return -1; } 1.3 返回插入位置 给定一个有序（非降序）数组A，若target在数组中出现，返回位置，若不存在，返回它应该插入的位置。 [cpp] view plain copy print? int?search(int?A[],?int?n,?int?target)?? {?? ????int?low?=?0,?high?=?n-1;?? ????while(low?=?high)?? ????{?? ????????//?注意：若使用(low+high)/2求中间位置容易溢出?? ????????int?mid?=?low+((high-low)1);??? ????????if(A[mid]?==?target)?? ????????????return?mid;?? ????????else?if(A[mid]??target)?? ????????????low?=?mid+1;?? ????????else?//?A[mid]??target?? ????????????high?=?mid-1;?? ????}?? ????return?-(low+1);?? }?? int search(int A[], int n, int target) { int low = 0, high = n