Leetcode-search in rotated Sorted array-rotation array Search-two points search + algebraic logic

https://oj.leetcode.com/problems/search-in-rotated-sorted-array/

A rotated array that requires a binary search query for a number. Modified binary search can be done. Note that a[l]<a[r] can be used to determine the l,r median distribution of numbers. In A[l]>a[r], there is a discontinuity in the middle. The position relationship between the midpoint and the center of rotation can be judged by a[mid]>a[r]. Then move L or R through a logical comparison. Draw a line chart to understand better.

Note that the binary search termination condition is l<r, and the l=mid+1 is always used when updating the L position. This avoids the cycle of death. Determines whether a query is queried after exiting the loop by judging A[l] and the target relationship.

classSolution { Public:    intSearchintA[],intNinttarget) {        intL=0; intr=n-1; intx=Target;  while(r>l) {            intMid= (L+R)/2; if(X==a[mid])returnmid; if(a[l]<A[r]) {                if(X<a[mid]) r=mid; ElseL=mid+1; }            Else{//Al>ar                if(a[mid]<A[r]) {                    if(X<a[mid]) r=mid; Else {                        if(X>a[r]) r=mid; ElseL=mid+1; }                }                Else {                    if(X>a[mid]) l=mid+1; Else {                        if(X>a[r]) r=mid; ElseL=mid+1; }                }            }        }        if(a[l]==x)returnl; return-1; }};

Leetcode-search in rotated Sorted array-rotation array Search-two points search + algebraic logic