41 lines
696 B
JavaScript
41 lines
696 B
JavaScript
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/**
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* 第k大的数
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* @param {array} arr
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* @param {number} k
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*/
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function kthNum(arr, k) {
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const len = arr.length;
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if (k > len) {
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return -1;
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}
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let p = partition(arr, 0, len - 1);
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while (p + 1 !== k) {
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if (p + 1 > k) {
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p = partition(arr, 0, p - 1);
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} else {
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p = partition(arr, p + 1, len - 1);
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}
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}
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return arr[p];
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}
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function partition(arr, start, end) {
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let i = start;
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let pivot = arr[end];
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for (let j = start; j < end; j++) {
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if (arr[j] > pivot) {
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swap(arr, i, j);
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i += 1;
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}
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}
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swap(arr, i, end);
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return i;
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}
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function swap(arr, i, j) {
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if (i === j) return;
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let tmp = arr[i];
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arr[i] = arr[j];
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arr[j] = tmp;
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}
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