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456-132Pattern.js
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456-132Pattern.js
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var find132pattern = function (nums) {
const n = nums.length;
const candidateI = [nums[0]],
candidateJ = [nums[0]];
for (let k = 1; k < n; ++k) {
const idxI = binarySearchFirst(candidateI, nums[k]);
const idxJ = binarySearchLast(candidateJ, nums[k]);
if (idxI >= 0 && idxJ >= 0) {
if (idxI <= idxJ) {
return true;
}
}
if (nums[k] < candidateI[candidateI.length - 1]) {
candidateI.push(nums[k]);
candidateJ.push(nums[k]);
} else if (nums[k] > candidateJ[candidateJ.length - 1]) {
const lastI = candidateI[candidateI.length - 1];
while (candidateJ.length && nums[k] > candidateJ[candidateJ.length - 1]) {
candidateI.pop();
candidateJ.pop();
}
candidateI.push(lastI);
candidateJ.push(nums[k]);
}
}
return false;
};
const binarySearchFirst = (candidate, target) => {
let low = 0,
high = candidate.length - 1;
if (candidate[high] >= target) {
return -1;
}
while (low < high) {
const mid = Math.floor((high - low) / 2) + low;
const num = candidate[mid];
if (num >= target) {
low = mid + 1;
} else {
high = mid;
}
}
return low;
};
const binarySearchLast = (candidate, target) => {
let low = 0,
high = candidate.length - 1;
if (candidate[low] <= target) {
return -1;
}
while (low < high) {
const mid = Math.floor((high - low + 1) / 2) + low;
const num = candidate[mid];
if (num <= target) {
high = mid - 1;
} else {
low = mid;
}
}
return low;
};