二分查找

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <iostream>
using namespace std;

/*
//1: 给定一个有序（不降序）数组arr，求最大的i使得arr[i]等于v，不存在则返回-1
int bisearch(char arr[][10], int begin, int end, char *v)
{
    int minIndex = begin;
    int maxIndex = end;
    int midIndex;

    while(minIndex < maxIndex - 1) {
        midIndex = minIndex + (maxIndex - minIndex) / 2;

        if(strcmp(arr[midIndex], v) <= 0)
            minIndex = midIndex;
        else
            maxIndex = midIndex;
    }

    //从最大索引开始判断
    if(!strcmp(arr[maxIndex], v))
        return maxIndex;
    else if(!strcmp(arr[minIndex], v))
        return minIndex;
    else
        return -1;
}
*/

/*
//2: 一个有序（不降序）数组arr，求任意一个i使得arr[i]等于v,不存在则返回-1
int bisearch(char (*arr)[10], int begin, int end, char *v)
{
    int minIndex = begin;
    int maxIndex = end;
    int midIndex;
    while(minIndex < maxIndex) {
       
       midIndex = minIndex + (maxIndex - minIndex) / 2;
       
       if(strcmp(*(arr + midIndex), v) < 0)
           minIndex = midIndex + 1;
       else if(strcmp(*(arr + midIndex), v) > 0)
           maxIndex = midIndex - 1;
       else
           return midIndex;
    }

    cout << "minIndex = " << minIndex << " maxIndex = " << maxIndex << endl;
    
    if(!strcmp(*(arr + minIndex), v))
        return minIndex;

    return -1;
}
*/

/*
//3:给定一个有序（不降序）数组arr，求最小的i使得arr[i]等于v，不存在则返回-1
int bisearch(char (*arr)[10], int begin, int end, char *v)
{
    int minIndex = begin;
    int maxIndex = end;
    int midIndex;

    while(minIndex < maxIndex - 1) {
        midIndex = minIndex + (maxIndex - minIndex) / 2;
        if(strcmp(*(arr + midIndex), v) < 0)
            minIndex = midIndex;
        else
            maxIndex = midIndex;
    }

    cout << "minIndex = " << minIndex << " maxIndex = " << maxIndex << endl;

    //从最小数开始判断
    if(!strcmp(*(arr + minIndex), v))
        return minIndex;
    else if(!strcmp(*(arr + maxIndex), v))
        return maxIndex;
    else
        return -1;
}
*/

/*
//4:给定一个有序（不降序）数组arr，求最大的i使得arr[i]小于v，不存在则返回-1
int bisearch(char (*arr)[10], int begin, int end, char *v)
{
    int minIndex = begin;
    int maxIndex = end;
    int midIndex;

    while(minIndex < maxIndex - 1) {
        midIndex = minIndex + (maxIndex - minIndex) / 2;
        if(strcmp(*(arr + midIndex), v) < 0)
            minIndex = midIndex;
        else
            maxIndex = midIndex;
    }

    //从最大数开始判断
    if(strcmp(*(arr + maxIndex), v) < 0)
        return maxIndex;
    else if(strcmp(*(arr + minIndex), v) < 0)
        return minIndex;
    else
        return -1;
}
*/


//5; 给定一个有序（不降序）数组arr，求最小的i使得arr[i]大于v，不存在则返回-1
int bisearch(char (*arr)[10], int begin, int end, char *v)
{
    int minIndex = begin;
    int maxIndex = end;
    int midIndex;

    while(minIndex < maxIndex - 1) {
        midIndex = minIndex + (maxIndex - minIndex) / 2;
        
        if(strcmp(*(arr + midIndex), v) <= 0)
            minIndex = midIndex;
        else
            maxIndex = midIndex;
    }

    //从小数开始判断
    if(strcmp(*(arr + minIndex), v) > 0)
        return minIndex;
    else if(strcmp(*(arr + maxIndex), v) > 0)
        return maxIndex;
    else
        return -1;
}



int main()
{
    char a[][10] = {"abc", "bcd", "bddaaa", "ddcd", "ddd", "ddd", "ddd", "ddd", "xxx", "xxxx"};
    char v[] = "dddd";
    int last = sizeof(a) / (sizeof(char) * 10);
    int index = bisearch(a, 0, last-1, v);
    printf("index of v is %d\n", index);

    return 0;
}