查找最后一个小于等于value的元素.cpp

#include <iostream>
using namespace std;

int binary_search(int a[], int n, int value)
{
    int l = 0, r = n - 1;
    while(l <= r)
    {
        int mid = l + ((r - l) >> 1);
        if(a[mid] <= value) {
            if(mid == n - 1 || a[mid + 1] > value) return mid;
            else    r = mid - 1;
        }
        else {
            l = mid + 1;
        }
    }

    return -1;
}