'commit'

C++专题课程/基础知识/折半查找.cpp

@@ -0,0 +1,75 @@
+#include<bits/stdc++.h>
+using namespace std;
+#define MAX 101
+void input(int num[]) {
+	int i;
+
+	srand((unsigned)time(NULL));
+	for(i=1; i<MAX; i++)
+		num[i]=rand()%100;
+}
+void output(int num[]) {
+	int i;
+
+	for(i=1; i<MAX; i++) {
+		printf("%5d", num[i]);
+		if(0==i%10)
+			printf("\n");
+	}
+}
+void sort(int num[], int low, int high) { /* quick sort */
+	int l, h;
+
+	if(low<high) {
+		l=low;
+		h=high;
+		num[0]=num[l]; /* save pivot */
+
+		while(l<h) {
+			while(l<h && num[h]>=num[0]) h--;
+			num[l]=num[h];
+			while(l<h && num[l]<=num[0]) l++;
+			num[h]=num[l];
+		}
+		num[l]=num[0]; /* insert pivot */
+
+		sort(num, low, l-1);
+		sort(num, l+1, high);
+	}
+}
+int find(int num[], int x, int low, int high) {
+	int mid;
+
+	while(low<=high) {
+		mid=(low+high)/2; /* find is OK */
+
+		if(x==num[mid])
+			return mid;
+		else if(x<num[mid])
+			high=mid-1;
+		else
+			low=mid+1;
+	}
+	return 0;
+}
+int main() {
+	int x, pos, num[MAX];
+	input(num);
+
+	printf("sort before... \n");
+	output(num);
+	sort(num, 1, MAX-1);
+	printf("sort after... \n");
+	output(num);
+
+	printf("Enter find num: ");
+	scanf("%d", &x);
+	pos=find(num, x, 1, MAX-1);
+	if(pos)
+		printf("OK! %d is found in pos: %d\n", x, pos);
+	else
+		printf("Sorry! %d is not found... in num\n", x);
+	return 0;
+}
+
+