二分模板2（进阶）

1 找到小于等于target的最大值

模板1

var search = function(nums, target) {
    let l = 0, r = nums.length - 1;
    while (l <= r) {
        let m = l + parseInt((r - l) / 2);
        if (nums[m] <= target) { // nums[m] < target, 目标在[m, r], 如果在m位，最终会进入l==r, 且target < nums[m]
            l = m + 1;
        }
        else { // target < nums[m], 目标在[l, m), 至少在m - 1
            r = m - 1;
        }
    }
    return r;
};

target是最小值时，r = -1
target是最大值时，r = nums.length - 1
所以，r的取值范围[-1, nums.length - 1];
模板2

var search = function(nums, target) {
    let l = -1, r = nums.length - 1;
    while (l < r) {
        let m = l + Math.ceil((r - l) / 2);
        if (nums[m] <= target) { // nums[m] < target, 目标在[m, r]
            l = m;
        }
        else { // target < nums[m], 目标在[l, m), 至少在m - 1
            r = m - 1;
        }
    }
    return l;
};

1 找到大于等于target的最小值

模板1

var search = function(nums, target) {
    let l = 0, r = nums.length - 1;
    while (l <= r) {
        let m = l + parseInt((r - l) / 2);
        if (nums[m] < target) { // nums[m] < target, 目标在(m, r], 至少在m + 1
            l = m + 1;
        }
        else { // target <= nums[m], 目标在[l, m],  如果在m位，最终会进入l==r, 且nums[m] < targrt
            r = m - 1;
        }
    }
    return l;
};

target是最小值时，r = 0
target是最大值时，r = nums.length
所以，r的取值范围[0, nums.length];
模板2

var search = function(nums, target) {
    let l = 0, r = nums.length;
    while (l < r) {
        let m = l + parseInt((r - l) / 2);
        if (nums[m] < target) { // nums[m] < target, 目标在(m, r], 至少在m + 1
            l = m + 1;
        }
        else { // target <= nums[m], 目标在[l, m]
            r = m;
        }
    }
    return l;
};