题目：

题解：

int upper_bound(int* vec, int vecSize, int target) {
    int low = 0, high = vecSize - 1;
    if (vec[high] >= target) {
        return -1;
    }
    while (low < high) {
        int mid = (high - low) / 2 + low;
        int num = vec[mid];
        if (num >= target) {
            low = mid + 1;
        } else {
            high = mid;
        }
    }
    return low;
}

int lower_bound(int* vec, int vecSize, int target) {
    int low = 0, high = vecSize - 1;
    if (vec[low] <= target) {
        return -1;
    }
    while (low < high) {
        int mid = (high - low + 1) / 2 + low;
        int num = vec[mid];
        if (num <= target) {
            high = mid - 1;
        } else {
            low = mid;
        }
    }
    return low;
}

bool find132pattern(int* nums, int numsSize) {
    int n = numsSize;
    int candidate_i[n], top_i = 0;
    int candidate_j[n], top_j = 0;
    candidate_i[top_i++] = nums[0];
    candidate_j[top_j++] = nums[0];

    for (int k = 1; k < n; ++k) {
        int it_i = upper_bound(candidate_i, top_i, nums[k]);
        int it_j = lower_bound(candidate_j, top_j, nums[k]);
        if (it_i != -1 && it_j != -1) {
            if (it_i <= it_j) {
                return true;
            }
        }

        if (nums[k] < candidate_i[top_i - 1]) {
            candidate_i[top_i++] = nums[k];
            candidate_j[top_j++] = nums[k];
        } else if (nums[k] > candidate_j[top_j - 1]) {
            int last_i = candidate_i[top_i - 1];
            while (top_j && nums[k] > candidate_j[top_j - 1]) {
                top_j--, top_i--;
            }
            candidate_i[top_i++] = last_i;
            candidate_j[top_j++] = nums[k];
        }
    }

    return false;
}