统计一个数字在排序数组中出现的次数。
function GetNumberOfK(data, k)
{
// write code here
return findIndex(data, k + 0.5) - findIndex(data, k - 0.5)
}
function findIndex(data, k) {
var start = 0, end = data.length - 1;
while(start <= end) {
var mid = (start + end) >> 1;
if(data[mid] > k){
end = mid - 1;
} else if(data[mid] < k) {
start = mid + 1;
}
}
return start;
}
//二分法分别找数字的开始和结束位置
function GetNumberOfK(data, k)
{
// write code here
if(findStart(data,k) == -1 && findEnd(data,k) == -1) return 0;
return findEnd(data,k) - findStart(data,k) + 1;
}
function findStart(data,k) {
var start = 0, end = data.length - 1;
while(start <= end) {
var mid = (start + end )>> 1;
if(data[mid] > k) {
end = mid - 1;
} else if(data[mid] < k) {
start = mid + 1;
} else if(mid - 1 >= 0 && data[mid - 1] == k) {
end = mid - 1;
} else {
return mid
}
}
return -1;
}
function findEnd(data,k) {
var start = 0, end = data.length - 1;
while(start <= end) {
var mid = (start + end )>> 1;
if(data[mid] > k) {
end = mid - 1;
} else if(data[mid] < k) {
start = mid + 1;
} else if(mid + 1 < data.length && data[mid + 1] == k) {
start = mid + 1;
} else {
return mid
}
}
return -1;
}