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solution.js
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solution.js
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/**
* @param {number[][]} mat
* @return {number}
*/
var smallestCommonElement = function (mat) {
const indexs = new Array(mat.length).fill(0);
const L = mat[0].length;
while (indexs[0] < L) {
const el = mat[0][indexs[0]];
// flag标记是否是等于el
let flag = true;
for (let i = 1; i < indexs.length; i++) {
// 该行最大的都比el小 不用看了
if (mat[i][L - 1] < el) {
return -1;
}
const index = binarySearch(mat[i], indexs[i], el);
if (mat[i][index] !== el) {
flag = false;
}
indexs[i] = index;
}
if (flag) {
return el;
}
// 其实可以优化,根据其他行的当前元素找在第一行的索引
indexs[0]++;
}
return -1;
};
// 找到>=target的最接近的元素对应索引
function binarySearch (arr, low, target) {
let high = arr.length - 1;
let rst = high;
while (low <= high) {
const mid = (low + high) >> 1;
if (arr[mid] < target) {
low = mid + 1;
} else {
rst = Math.min(rst, mid);
high = mid - 1;
}
}
return rst;
}