1：TwoSum(如果两个和为某个数，找出这俩数的位置)

Bertha 。 2021-12-10 15:11 225阅读 0赞

package leetcode;
    
    import java.util.HashMap;
    import java.util.Map;
    
    /**
     * @author mercy
     *Example:
     *Given nums = [2, 7, 11, 15], target = 9,
     *Because nums[0] + nums[1] = 2 + 7 = 9,
     *return [0, 1].
     */
    public class TwoSum {
    	public static void main(String[] args) { int[] nums={ 2,0,4,9,5,7,10,9}; int target=12; int[] arr=twoSum1(nums,target); System.out.println(arr[0]+"--"+arr[1]); } public static int[] twoSum(int[] nums, int target) { Map<Integer,Integer> map=new HashMap<>(); for(int i=0;i<nums.length;i++){ map.put(nums[i], i); } for(int i=0;i<nums.length;i++){ int other=target-nums[i]; if(map.containsKey(other)&&map.get(other)!=i){ return new int[] { i, map.get(other) }; } } throw new IllegalArgumentException("No two sum solution"); } /** * @param nums * @param target * @return * 用Map方法 * @author mercy */ public static int[] twoSum1(int[] nums, int target) { Map<Integer,Integer> map=new HashMap<>(); for(int i=0;i<nums.length;i++){ int other=target-nums[i]; if(map.containsKey(other)){ return new int[]{ map.get(other),i}; } map.put(nums[i], i); } throw new IllegalArgumentException("No two sum solution"); } /** * @param nums * @param target * @return * 传统的方法 * @author mercy */ public static int[] twoSum2(int[] nums, int target) { for(int i=0;i<nums.length;i++){ for(int j=i+1;j<nums.length;j++){ if(nums[j]==target-nums[i]){ return new int[] {i,j}; } } } throw new IllegalArgumentException("No two sum solution"); } }

转载于:https://www.cnblogs.com/JAYIT/p/6956072.html