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3Sum_Closest.cpp
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3Sum_Closest.cpp
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// Given an array S of n integers, find three integers in S
// such that the sum is closest to a given number, target.
// Return the sum of the three integers.
// You may assume that each input would have exactly one solution.
// For example, given array S = {-1 2 1 -4}, and target = 1.
// The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).
class Solution {
public:
int threeSumClosest(vector<int> &num, int target) {
int size = num.size();
if (size < 3)
return 0;
sort(num.begin(), num.end());
int closest = num[0]+num[1]+num[2];
for (int i = 0; i < size-2; i++) {
int start = i+1;
int end = size-1;
while (start < end) {
int sum = num[i]+num[start]+num[end];
if (sum == target)
return target;
if (abs(closest-target) > abs(sum-target))
closest = sum;
if (sum > target)
end--;
else
start++;
}
}
return closest;
}
};