[JS]矩阵查找

这道题本质还是二分查找，和普通的有所不同的是要进行两次。因为每列每行都是有序的，所以在定位行以后再定位列。

function searchMatrix( matrix ,  target ) {
    // write code here
    let up = 0,down = matrix.length-1
    let row = 0

    while(up<=down){//定位行
        let mid = Math.floor((up+down)/2)
        if(matrix[mid][0]<=target){
            if(mid==matrix.length-1||matrix[mid+1][0]>target){
                row = mid
                break
            }else{
                up = mid+1
                row = up
            }
        }else{
            down = mid-1
            row = down
        }
    }
    if(row==-1) return false//如果没有找到直接返回false
    let left = 0,right = matrix[0].length-1

    while(left<=right){//定位列

        let mid = Math.floor((left+right)/2)
        if(matrix[row][mid]<=target){
            if(matrix[row][mid]==target) return true//找到
            else{
                left = mid+1
            }
        }else{
            right = mid-1
        }

    }


    return false

}