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The implementation of binary search is not complicated, but it is a vivid illustration of the power of divide-and-conquer.
Here is the code
1 int binarySearch(int a[], int n, int x){ 2 int lo = 0; 3 int hi = n-1; 4 while(lo<=hi){ 5 int mid = lo + (hi-lo)/2; 6 if (a[mid] == x) return mid; 7 else if(a[mid]<x) 8 lo = mid + 1; 9 else hi = mid - 1; 10 } 11 return -1; //not found; 12 }
Pay attention to line 5: we can‘t use ‘mid = (lo+hi)/2‘ here. we may have over-flow if (lo+hi)>231 - 1.
More details about this subtle bug.
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原文地址：http://www.cnblogs.com/charmingblog/p/5202590.html
