16.3Sum Closest

题目链接：3sum-closest

import java.util.Arrays;/** *  * 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). * */public class ThreeSumClosest {//超时    static int threeSumClosest(int[] num, int target) {        Arrays.sort(num);    int left = 0;    int right = num.length - 1;    int minGap = Integer.MAX_VALUE;    int closest = 0;    while(right >= 2 ) {    while(left < right - 1) {    for (int mid = left + 1; mid < right; mid++) {int gap =Math.abs(num[left] + num[mid] + num[right] - target) ;if(gap < minGap) {closest = num[left] + num[mid] + num[right];minGap = gap;}}        int preLeft = num[left];    while(left < right - 1 && num[left] == preLeft) left++;    }        left = 0;    int preRight = num[right];    while(right >= 2 && num[right] == preRight)right --;    }      return closest;    }        //超时    static int threeSumClosest1(int[] num, int target) {        Arrays.sort(num);    int left = 0;    int right = num.length - 1;    int minGap = Integer.MAX_VALUE;    int closest = 0;    while(right >= 2 ) {    while(left < right - 1) {    boolean isFirst = true;    int preGap = 0;    for (int mid = left + 1; mid < right; mid++) {int gap =Math.abs(num[left] + num[mid] + num[right] - target) ;if(isFirst) {preGap = gap;isFirst = false;}if(gap > preGap) break;if(gap < minGap) {closest = num[left] + num[mid] + num[right];minGap = gap;}}        int preLeft = num[left];    while(left < right - 1 && num[left] == preLeft) left++;    }        left = 0;    int preRight = num[right];    while(right >= 2 && num[right] == preRight)right --;    }      return closest;    }        // accepted    static int threeSumClosest2(int[] num, int target) {    //    120 / 120 test cases passed.//    Status: Accepted//    Runtime: 278 ms//    Submitted: 0 minutes ago    Arrays.sort(num);    int minGap = Integer.MAX_VALUE;    int closest = 0;    for(int left = 0; left < num.length - 2; left ++) {    int mid = left + 1;    int right = num.length - 1;    while(mid < right) {    int sum = num[left] + num[mid] + num[right];    if(Math.abs(sum - target) < minGap) {    closest = sum;    minGap = Math.abs(sum - target);    }    if(sum < target) mid++;    else right --;    }    }          return closest;    }public static void main(String[] args) {System.out.println(threeSumClosest2(new int[]{43,75,-90,47,-49,72,17,-31,-68,-22,-21,-30,65,88,-75,23,97,-61,53,87,-3,33,20,51,-79,43,80,-9,34,-89,-7,93,43,55,-94,29,-32,-49,25,72,-6,35,53,63,6,-62,-96,-83,-73,66,-11,96,-90,-27,78,-51,79,35,-63,85,-82,-15,100,-82,1,-4,-41,-21,11,12,12,72,-82,-22,37,47,-18,61,60,55,22,-6,26,-60,-42,-92,68,45,-1,-26,5,-56,-1,73,92,-55,-20,-43,-56,-15,7,52,35,-90,63,41,-55,-58,46,-84,-92,17,-66,-23,96,-19,-44,77,67,-47,-48,99,51,-25,19,0,-13,-88,-10,-67,14,7,89,-69,-83,86,-70,-66,-38,-50,66,0,-67,-91,-65,83,42,70,-6,52,-21,-86,-87,-44,8,49,-76,86,-3,87,-32,81,-58,37,-55,19,-26,66,-89,-70,-69,37,0,19,-65,38,7,3,1,-96,96,-65,-52,66,5,-3,-87,-16,-96,57,-74,91,46,-79,0,-69,55,49,-96,80,83,73,56,22,58,-44,-40,-45,95,99,-97,-22,-33,-92,-51,62,20,70,90, 284}, 1));}}