求一个数组的最长递减子序列 比如{9，4，3，2，5，4，3，2}的最长递减子序列为{9，5，4，3，2}。

int binaryFind(int* lis, int target, int end) {
int low = 0;
int high = end;
while (low <= high) {
int mid = (low + high) / 2;
if (target < lis[mid]) {
low = mid + 1;
} else {
high = mid - 1;
}
}
return low;
}

int* findLongestSubquence(int* arr, int len, int &maxLen) {
if (!arr || len == 0) {
return NULL;
}
//0~i元素递减排序
int* lis = new int[len];
//记录i元素结尾的递减子序列长度
int* lds = new int[len];
memset(lis, 0, sizeof(int) * len);
memset(lds, 0, sizeof(int) * len);

maxLen = 1;
lis[0] = arr[0];
lds[0] = 1;

for (int i = 1; i < len; ++i) {
//递减的二分查找
int pos = binaryFind(lis, arr[i], maxLen - 1);
lis[pos] = arr[i];
//以该元素结尾的最长递减序列的长度
lds[i] = pos + 1;

if (pos >= maxLen) {
maxLen++;
}
}

int curLen = maxLen;
//还原最长递减子序列
for (int i = len - 1; i >= 0; --i) {
if (lds[i] == curLen) {
lis[curLen - 1] = arr[i];
curLen--;
if (curLen == 0) {
break;
}
}
}
return lis;
}