refactor

9 Algorithms Job Interview/codes/7 bianrytree/binary_search.c

@@ -0,0 +1,70 @@
+
+
+#include "stdio.h"
+
+int binary_search_first(int *a,int length,int key){
+
+	int low=0;
+	int high = length-1;
+	int mid = 0;
+
+	while(low<high){
+
+		mid = (low+high)/2;
+		if (a[mid]>=key)//往左找
+		{
+			high = mid;
+		}else{
+
+			low = mid+1;
+		}
+
+	}
+	return high;
+
+}
+
+int binary_search_last(int *a,int length,int key){
+
+	int low = 0;
+	int high = length -1;
+	int mid = 0;
+
+	while(low<high){
+
+		mid = (low+high+1)/2;
+		if (a[mid]<=key)// 往右找	
+		{
+			low=mid;
+		}else{
+			high = mid-1;
+		}
+
+	}
+
+	return low;
+}
+
+
+int element_appear_times(int *a,int length,int key){
+
+	printf("(%d) first appear at index %d\n",key,binary_search_first(a,length,key));
+	printf("(%d) last appear at index %d\n",key,binary_search_last(a,length,key));
+	return binary_search_last(a,length,key)-binary_search_first(a,length,key)+1;
+
+}
+
+
+int main(){
+
+
+	int a[] = {2,3,4,4,4,4,4,5,5,7,7,11,11,11,11,11,32,32,54};
+
+	printf("(2)appear times = %d\n", element_appear_times(a,sizeof(a)/sizeof(int),2) );
+	printf("(4)appear times = %d\n", element_appear_times(a,sizeof(a)/sizeof(int),4) );
+	printf("(11)appear times = %d\n", element_appear_times(a,sizeof(a)/sizeof(int),11) );
+	printf("(36)appear times = %d\n", element_appear_times(a,sizeof(a)/sizeof(int),36) );
+	printf("(54)appear times = %d\n", element_appear_times(a,sizeof(a)/sizeof(int),54) );
+	return 0;
+}
+