/**
* @param {number[][]} matrix
* @param {number} k
* @return {number}
*/
let kthSmallest = function (matrix, k) {
let maxY = matrix.length
let sorted = []
let points = []
for (let i = 0; i < maxY; i++) {
points[i] = 0
}
while (sorted.length < k) {
let min = Infinity
let minY
for (let y = 0; y < maxY; y++) {
let point = points[y]
let num = matrix[y][point]
if (num < min) {
min = num
minY = y
}
}
sorted.push(min)
// 选中最小项的x指针右移
points[minY]++
}
return sorted[sorted.length - 1]
};
